Cant' complete the user task using form created by Kie Server

Issue

• When create a form generated by kie-server using REST API and exist a complex process variable is not possible complete the user task
  • Url to provide the form.

http://localhost:8080/kie-server/services/rest/server/containers/container_1.0.0-SNAPSHOT/forms/tasks/2/content?renderer=patternfly

• Get the error below.

488 ERROR [org.kie.server.remote.rest.jbpm.UserTaskResource] (default task-91) Unexpected error during processing [TaskUser:14 - TaskUser:41] -- null: org.jbpm.workflow.instance.WorkflowRuntimeException: [TaskUser14 - TaskUser:41] -- null
    at org.jbpm.workflow.instance.impl.NodeInstanceImpl.executeAction(NodeInstanceImpl.java:230)
    at org.jbpm.workflow.instance.impl.ExtendedNodeInstanceImpl.triggerEvent(ExtendedNodeInstanceImpl.java:56)
    at org.jbpm.workflow.instance.impl.ExtendedNodeInstanceImpl.triggerCompleted(ExtendedNodeInstanceImpl.java:43)
    at org.jbpm.workflow.instance.node.StateBasedNodeInstance.triggerCompleted(StateBasedNodeInstance.java:393)
    at org.jbpm.workflow.instance.node.StateBasedNodeInstance.triggerCompleted(StateBasedNodeInstance.java:353)
    at org.jbpm.workflow.instance.node.WorkItemNodeInstance.triggerCompleted(WorkItemNodeInstance.java:307)
    at org.jbpm.workflow.instance.node.HumanTaskNodeInstance.triggerCompleted(HumanTaskNodeInstance.java:94)
    at org.jbpm.workflow.instance.node.WorkItemNodeInstance.workItemCompleted(WorkItemNodeInstance.java:451)
    at org.jbpm.workflow.instance.node.WorkItemNodeInstance.signalEvent(WorkItemNodeInstance.java:421)
    at org.jbpm.workflow.instance.impl.WorkflowProcessInstanceImpl.signalEvent(WorkflowProcessInstanceImpl.java:616)
    at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.completeWorkItem(JPAWorkItemManager.java:167)