A user with no writing rights can D&D in a workspace

He gets the error below. But shouldn't he be told that he has no writing rights and so can't D&D any document or folder in the workspace ?

exception

javax.servlet.ServletException: Could not find Stateful bean: 3j011-ll7ymq-f10hezis-1-f10u84aa-3k7
javax.faces.webapp.FacesServlet.service(FacesServlet.java:256)
org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:100)
org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:147)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._invokeDoFilter(TrinidadFilterImpl.java:209)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._doFilterImpl(TrinidadFilterImpl.java:166)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl.doFilter(TrinidadFilterImpl.java:139)
org.apache.myfaces.trinidad.webapp.TrinidadFilter.doFilter(TrinidadFilter.java:92)
org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:96)
org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:220)
org.nuxeo.ecm.platform.ui.web.rest.FancyURLFilter.doFilter(FancyURLFilter.java:67)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)

root cause

javax.ejb.EJBNoSuchObjectException: Could not find Stateful bean: 3j011-ll7ymq-f10hezis-1-f10u84aa-3k7
org.jboss.ejb3.cache.simple.SimpleStatefulCache.get(SimpleStatefulCache.java:266)
org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:59)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.security.RoleBasedAuthorizationInterceptor.invoke(RoleBasedAuthorizationInterceptor.java:167)
org.jboss.ejb3.security.RoleBasedAuthorizationInterceptor.invoke(RoleBasedAuthorizationInterceptor.java:100)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:78)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:47)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.stateful.StatefulContainer.dynamicInvoke(StatefulContainer.java:297)
org.jboss.ejb3.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:59)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.stateful.StatefulRemoteProxy.invoke(StatefulRemoteProxy.java:133)
$Proxy162.getPrincipal(Unknown Source)
org.nuxeo.ecm.webapp.action.WebActionsBean.createActionContext(WebActionsBean.java:144)
org.nuxeo.ecm.webapp.action.WebActionsBean.getActionsList(WebActionsBean.java:120)
sun.reflect.GeneratedMethodAccessor455.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:112)
org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:166)
org.nuxeo.ecm.webapp.shield.ErrorHandlingInterceptor.invokeAndWrapExceptions(ErrorHandlingInterceptor.java:62)
sun.reflect.GeneratedMethodAccessor167.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:118)
org.jboss.seam.intercept.EJBInvocationContext.proceed(EJBInvocationContext.java:37)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:55)
org.jboss.seam.interceptors.BijectionInterceptor.bijectNonreentrantComponent(BijectionInterceptor.java:79)
org.jboss.seam.interceptors.BijectionInterceptor.bijectComponent(BijectionInterceptor.java:58)
sun.reflect.GeneratedMethodAccessor162.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.ManagedEntityIdentityInterceptor.aroundInvoke(ManagedEntityIdentityInterceptor.java:36)
sun.reflect.GeneratedMethodAccessor166.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.OutcomeInterceptor.interceptOutcome(OutcomeInterceptor.java:21)
sun.reflect.GeneratedMethodAccessor161.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.ConversationInterceptor.endOrBeginLongRunningConversation(ConversationInterceptor.java:52)
sun.reflect.GeneratedMethodAccessor159.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.BusinessProcessInterceptor.manageBusinessProcessContext(BusinessProcessInterceptor.java:51)
sun.reflect.GeneratedMethodAccessor158.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.MethodContextInterceptor.aroundInvoke(MethodContextInterceptor.java:27)
sun.reflect.GeneratedMethodAccessor157.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.intercept.RootInterceptor.createSeamInvocationContext(RootInterceptor.java:144)
org.jboss.seam.intercept.RootInterceptor.invokeInContexts(RootInterceptor.java:129)
org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:102)
org.jboss.seam.intercept.SessionBeanInterceptor.aroundInvoke(SessionBeanInterceptor.java:50)
sun.reflect.GeneratedMethodAccessor165.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:118)
org.jboss.ejb3.interceptor.EJB3InterceptorsInterceptor.invoke(EJB3InterceptorsInterceptor.java:63)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.entity.ExtendedPersistenceContextPropagationInterceptor.invoke(ExtendedPersistenceContextPropagationInterceptor.java:57)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.entity.TransactionScopedEntityManagerInterceptor.invoke(TransactionScopedEntityManagerInterceptor.java:54)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsInterceptor.java:47)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:79)
org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java:197)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:76)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:81)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.security.RoleBasedAuthorizationInterceptor.invoke(RoleBasedAuthorizationInterceptor.java:167)
org.jboss.ejb3.security.RoleBasedAuthorizationInterceptor.invoke(RoleBasedAuthorizationInterceptor.java:100)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:78)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:47)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
org.jboss.ejb3.stateful.StatefulContainer.localInvoke(StatefulContainer.java:188)
org.jboss.ejb3.stateful.StatefulLocalProxy.invoke(StatefulLocalProxy.java:98)
$Proxy303.getActionsList(Unknown Source)
org.nuxeo.ecm.platform.ui.web.api.WebActions$$FastClassByCGLIB$$91155092.invoke(<generated>)
net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
org.jboss.seam.intercept.RootInvocationContext.proceed(RootInvocationContext.java:45)
org.jboss.seam.intercept.ClientSideInterceptor$1.proceed(ClientSideInterceptor.java:74)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:55)
org.jboss.seam.interceptors.RemoveInterceptor.removeIfNecessary(RemoveInterceptor.java:40)
sun.reflect.GeneratedMethodAccessor164.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.interceptors.ExceptionInterceptor.handleExceptions(ExceptionInterceptor.java:39)
sun.reflect.GeneratedMethodAccessor156.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
org.jboss.seam.intercept.RootInterceptor.createSeamInvocationContext(RootInterceptor.java:144)
org.jboss.seam.intercept.RootInterceptor.invokeInContexts(RootInterceptor.java:129)
org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:102)
org.jboss.seam.intercept.ClientSideInterceptor.interceptInvocation(ClientSideInterceptor.java:83)
org.jboss.seam.intercept.ClientSideInterceptor.intercept(ClientSideInterceptor.java:52)
org.jboss.seam.intercept.Proxy$$EnhancerByCGLIB$$668289dc.getActionsList(<generated>)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
com.sun.el.parser.AstValue.invoke(AstValue.java:151)
com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:283)
org.jboss.seam.ui.facelet.MethodExpressionHelper.invokeTheExpression(MethodExpressionHelper.java:102)
org.jboss.seam.ui.facelet.ParamMethodExpression.invoke(ParamMethodExpression.java:62)
com.sun.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:68)
org.nuxeo.ecm.platform.ui.web.binding.MethodValueExpression.getValue(MethodValueExpression.java:88)
com.sun.el.parser.AstIdentifier.getValue(AstIdentifier.java:61)
com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:192)
com.sun.facelets.el.TagValueExpression.getValue(TagValueExpression.java:71)
javax.faces.component.UIData.getValue(UIData.java:582)
org.apache.myfaces.component.html.ext.HtmlDataTableHack.createDataModel(HtmlDataTableHack.java:437)
org.apache.myfaces.component.html.ext.HtmlDataTableHack.getDataModel(HtmlDataTableHack.java:414)
org.apache.myfaces.component.html.ext.HtmlDataTableHack.getRowCount(HtmlDataTableHack.java:87)
org.apache.myfaces.custom.datalist.HtmlListRenderer.encodeChildren(HtmlListRenderer.java:120)
javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:809)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:886)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:892)
javax.faces.component.UIComponent.encodeAll(UIComponent.java:892)
com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:578)
org.apache.myfaces.trinidadinternal.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:181)
org.jboss.seam.jsf.SeamViewHandler.renderView(SeamViewHandler.java:59)
org.ajax4jsf.framework.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:108)
org.ajax4jsf.framework.ajax.AjaxViewHandler.renderView(AjaxViewHandler.java:229)
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:106)
com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:251)
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:144)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:245)
org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:100)
org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:147)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._invokeDoFilter(TrinidadFilterImpl.java:209)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._doFilterImpl(TrinidadFilterImpl.java:166)
org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl.doFilter(TrinidadFilterImpl.java:139)
org.apache.myfaces.trinidad.webapp.TrinidadFilter.doFilter(TrinidadFilter.java:92)
org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:96)
org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:220)
org.nuxeo.ecm.platform.ui.web.rest.FancyURLFilter.doFilter(FancyURLFilter.java:67)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)