Fix possible NPE in class 'UITypesConfigurationActions'

diff --git a/nuxeo-features/localconf/nuxeo-localconf-web/src/main/java/org/nuxeo/ecm/localconf/UITypesConfigurationActions.java b/nuxeo-features/localconf/nuxeo-localconf-web/src/main/java/org/nuxeo/ecm/localconf/UITypesConfigurationActions.java
index dfb7f99..5982c47 100644
--- a/nuxeo-features/localconf/nuxeo-localconf-web/src/main/java/org/nuxeo/ecm/localconf/UITypesConfigurationActions.java
+++ b/nuxeo-features/localconf/nuxeo-localconf-web/src/main/java/org/nuxeo/ecm/localconf/UITypesConfigurationActions.java
@@ -28,6 +28,8 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.jboss.seam.annotations.In;
 import org.jboss.seam.annotations.Install;
 import org.jboss.seam.annotations.Name;
@@ -55,6 +57,8 @@ public class UITypesConfigurationActions implements Serializable {
 
     private static final long serialVersionUID = 1L;
 
+    private static final Log log = LogFactory.getLog(UITypesConfigurationActions.class);
+    
     @In(create = true)
     protected Map<String, String> messages;
 
@@ -87,7 +91,15 @@ public class UITypesConfigurationActions implements Serializable {
         @Override
         public int compare(Type type1, Type type2) {
             String label1 = messages.get(type1.getLabel());
+            if (label1 == null) {
+                log.error("No label for " + type1.getId());
+                label1 = type1.getId();
+            }
             String label2 = messages.get(type2.getLabel());
+            if (label2 == null) {
+                log.error("No label for " + type2.getId());
+                label2 = type2.getId();
+            }
             return label1.compareTo(label2);
         }
     }