AEM 6.0 to 6.3 Upgrade - Null pointer exception while invoking method AbstractAssetWorkflowProcess.getAssetFromPayload

Hi,

We are in the process of upgrade from 6.0 to 6.3. While running the workflow, I am getting a Null Pointer Exception as below

Caused by: java.lang.NullPointerException: null        at
com.day.cq.dam.commons.process.AbstractAssetWorkflowProcess.getResourceResolver(AbstractAssetWorkflowProcess.java:255)        at com.day.cq.dam.commons.process.AbstractAssetWorkflowProcess.getAssetFromPayload(AbstractAssetWorkflowProcess.java:91)

        at
com.cisco.wem.author.rendition.workflow.ValidateUserProcess.execute(ValidateUserProcess.java:61)

        at
com.day.cq.workflow.compatibility.CQWorkflowProcessRunner.execute(CQWorkflowProcessRunner.java:93)        ... 9 common frames omitted

These are the imports:

com.day.cq.dam.commons.process.AbstractAssetWorkflowProcess;

com.day.cq.workflow.WorkflowException;

com.day.cq.workflow.WorkflowSession;

com.day.cq.workflow.exec.Route;

com.day.cq.workflow.exec.WorkItem;

com.day.cq.workflow.exec.WorkflowProcess;

com.day.cq.workflow.metadata.MetaDataMap;

And this is the code snippet

class ValidateUserProcess extends AbstractAssetWorkflowProcess implements WorkflowProcess {

void execute(WorkItem workItem, WorkflowSession workflowSession, MetaDataMap metaData) throws WorkflowException {

try {

if (null != asset) {

Asset asset = getAssetFromPayload(workItem, workflowSession.getSession());

...

Appreciate any inputs

Thanks

- Atul