Cannot add/change values in a stringlist, in a Task, from WebUI

Have 3 groups

• administrators
• writer
• translator
  For the test, you can just put Administrator in writer and in translator

Have a workflow:

• A workflow variable
  • Name: theAssignees
  • Type either String or User/Group
  • multivalued
  • Set a default value to group:writer group:editor (not: space separated values are the way to initialize a stringlist)

• First task:
  • "Approve" task
  • Assigned (Assignees expression) to workflowInitiator
  • In "Task properties“ > Variables > "Workflow Variables Editable in this Task" => add theAssignees
  • In "Task properties“ > Variables, delete the assignees variable that is created by default
  • In the "Form" (for JSF tets), add theAssignees
  • Make sure to use a Multi Users/groups Suggestion and to set its Use prefixed reference to yes

• Second task
  • Type "Multiple Tasks"
  • Assigned (Assignees expression) to

    WorkflowVariables["theAssignees"]
    

  • In "Task properties“ > Variables, delete the assignees variable that is created by default

• In WebUI configure the 2 tasks
  • For the first one, make sure to use a nuxeo-user-suggestion and check its prefixed property
  • Configure second task, but nothing more to do there

Deploy the project:

• In JSF
  • Start the workflow on a document.
  • Add a group to the list, like administrators
  • Go to next task
  • => No problem

• In WebUI
  • Start the workflow on a document.
  • Add a group to the list, like administrators
  • Go to next task
  • Bug. In server.log:

    2018-07-06 18:24:18,397 ERROR [http-nio-0.0.0.0-8080-exec-15] [org.nuxeo.ecm.webengine.app.WebEngineExceptionMapper] java.lang.NullPointerException
    java.lang.NullPointerException
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.getScalarPropertyValue(DocumentPropertiesJsonReader.java:198)
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.fillScalarProperty(DocumentPropertiesJsonReader.java:155)
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.fillListProperty(DocumentPropertiesJsonReader.java:242)
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.readProperty(DocumentPropertiesJsonReader.java:135)
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.read(DocumentPropertiesJsonReader.java:120)
    	at org.nuxeo.ecm.core.io.marshallers.json.document.DocumentPropertiesJsonReader.read(DocumentPropertiesJsonReader.java:85)
    	at org.nuxeo.ecm.core.io.marshallers.json.AbstractJsonReader.read(AbstractJsonReader.java:79)
    	at org.nuxeo.ecm.core.io.marshallers.json.AbstractJsonReader.readEntity(AbstractJsonReader.java:129)
    	at org.nuxeo.ecm.platform.routing.core.io.TaskCompletionRequestJsonReader.getVariables(TaskCompletionRequestJsonReader.java:134)
    	at org.nuxeo.ecm.platform.routing.core.io.TaskCompletionRequestJsonReader.readEntity(TaskCompletionRequestJsonReader.java:117)
    	at org.nuxeo.ecm.platform.routing.core.io.TaskCompletionRequestJsonReader.readEntity(TaskCompletionRequestJsonReader.java:58)
    	at org.nuxeo.ecm.core.io.marshallers.json.EntityJsonReader.read(EntityJsonReader.java:65)
    	at org.nuxeo.ecm.core.io.marshallers.json.AbstractJsonReader.read(AbstractJsonReader.java:79)
    

NOTE: If you don't change the default list, all is good.

Tested with 9.10HF11 on Chrome only