Invalid reference in diagram interchange definition

Hello,
I am trying to create a CMMN model using the web modeler. I tried to create a simple model with a case and a human task inside. When I validate it the system give me invalid reference. I also receive a NullPointerException.
Am I missing something? Do you have a sample model that should work?

immagine

java.lang.NullPointerException: null
        at org.flowable.editor.language.json.converter.BpmnJsonConverter.processJsonElements(BpmnJsonConverter.java:730) [flowable-json-converter-6.4.1.jar:6.4.1]
        at org.flowable.editor.language.json.converter.BpmnJsonConverter.convertToBpmnModel(BpmnJsonConverter.java:631) [flowable-json-converter-6.4.1.jar:6.4.1]
        at org.flowable.editor.language.json.converter.BpmnJsonConverter.convertToBpmnModel(BpmnJsonConverter.java:459) [flowable-json-converter-6.4.1.jar:6.4.1]
        at org.flowable.ui.modeler.rest.app.ModelValidationRestResource.validate(ModelValidationRestResource.java:41) [flowable-ui-modeler-rest-6.4.1.jar:6.4.1]
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]
        at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/CMMN/20151109/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:flowable="http://flowable.org/cmmn" xmlns:cmmndi="http://www.omg.org/spec/CMMN/20151109/CMMNDI" xmlns:dc="http://www.omg.org/spec/CMMN/20151109/DC" xmlns:di="http://www.omg.org/spec/CMMN/20151109/DI" targetNamespace="http://www.flowable.org/casedef">
  <case id="test2" name="test2" flowable:initiatorVariableName="initiator">
    <casePlanModel id="casePlanModel" flowable:includeInStageOverview="false">
      <planItem id="planItem1" definitionRef="sid-3359175E-CE8A-4168-919B-2B1F9E1C8851"></planItem>
      <humanTask id="sid-3359175E-CE8A-4168-919B-2B1F9E1C8851"></humanTask>
    </casePlanModel>
  </case>
  <cmmndi:CMMNDI>
    <cmmndi:CMMNDiagram id="CMMNDiagram_test2">
      <cmmndi:CMMNShape id="CMMNShape_casePlanModel" cmmnElementRef="casePlanModel">
        <dc:Bounds height="714.0" width="718.0" x="40.0" y="40.0"></dc:Bounds>
        <cmmndi:CMMNLabel></cmmndi:CMMNLabel>
      </cmmndi:CMMNShape>
      <cmmndi:CMMNShape id="CMMNShape_planItem1" cmmnElementRef="planItem1">
        <dc:Bounds height="80.0" width="100.0" x="272.5" y="181.0"></dc:Bounds>
        <cmmndi:CMMNLabel></cmmndi:CMMNLabel>
      </cmmndi:CMMNShape>
    </cmmndi:CMMNDiagram>
  </cmmndi:CMMNDI>
</definitions>

Same happening to me in 6.4.2. Diagram pretty much empty, but shows warning about invalid reference to casePlanModel. I tried with samples from the internet and one from bpmn.io and always the same. Model looks to be valid - what could go wrong with an empty case plan - but Flowable validation gives warning. At least it’s not fatal.

Good catch, the reason is that validation isn’t added for the cmmn model (and it tries to parse it as a bpmn model). Applied a quick-fix here to avoid that happens: https://github.com/flowable/flowable-engine/commit/2203618a74d599de99e5154036ce836132691061