Unlock Payload Process throwing Null Pointer Exception

Hi,

We are upgrading from AEM 6.0 to AEM 6.2 . I see that Unlock Payload Process in the custom workflow is throwing Null Pointer Exception in Dynamic Participant step.

This custom workflow is triggered  by a scheduler  as below  and the session object  passed to create the workflow is obtained from serviceResourceResolver.

Can someone suggest how to resolve this.

  WorkflowSession wfSession = workflowService.getWorkflowSession(session);

        // Get the workflow model

        WorkflowModel wfModel = wfSession.getModel(wfModelDefn);

        if (wfModel != null) {

            // Get the workflow data

            // The first param in the newWorkflowData method is the payloadType.  Just a fancy name to let it know what type of workflow it is working with.

            WorkflowData wfData = wfSession.newWorkflowData("JCR_PATH", absContentPath);

            if (wfData != null) {

                // Run the Workflow.

                wfSession.startWorkflow(wfModel, wfData);

                LOG.debug("Workflow started for for mlc review : {}", absContentPath);

            }

Failure Messagejava.lang.NullPointerException

StepUnlock Payload Process

Failure Stackcom.adobe.granite.workflow.WorkflowException: java.lang.NullPointerException
at com.adobe.granite.workflow.core.advance.ParticipantNodeHandler.doTransition(ParticipantNodeHandler.java:198)
at com.adobe.granite.workflow.core.advance.AdvanceUtil.transitionFrom(AdvanceUtil.java:143)
at com.adobe.granite.workflow.core.WorkflowSessionImpl.completeInternal(WorkflowSessionImpl.java:951)
at com.adobe.granite.workflow.core.job.HandlerBase.complete(HandlerBase.java:507)
at com.adobe.granite.workflow.core.job.JobHandler.process(JobHandler.java:348)
at org.apache.sling.event.impl.jobs.JobConsumerManager$JobConsumerWrapper.process(JobConsumerManager.java:500)
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.startJob(JobQueueImpl.java:291)
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.access$100(JobQueueImpl.java:58)
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl$1.run(JobQueueImpl.java:227)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException