Getting org.eclipse.core.runtime.AssertionFailedException Wh

I may not be doing this the right way, but I am getting the following
xception when trying to move an existing workitem into the "In Progress"
state. Why am I getting this exception? Thanks.

Sample code:

.....................................

IWorkItemClient workItemClient = (IWorkItemClient)
repo.getClientLibrary(IWorkItemClient.class);

IAuditableClient iAuditableClient = (IAuditableClient)
repo.getClientLibrary(IAuditableClient.class);

IWorkItem workItem = workItemClient.findWorkItemById(defectId,
IWorkItem.DEFAULT_PROFILE, null);

System.out.println("**********************" + workItem.getId());
System.out.println("**********************" +
workItem.getHTMLSummary().toString());

CommonWorkItemOperation operation = new CommonWorkItemOperation(null,
transaction, getParameterFlags(), repo, area, workItemClient,
iAuditableClient);

operation.run(workItem, null); -------------------------->
line where exception is thrown


........................

WorkItemOperation class execute(..) method:

protected void execute(WorkItemWorkingCopy workingCopy, IProgressMonitor
monitor) throws TeamRepositoryException {

try {
updateWorkItem(transaction, artifactFlags, workingCopy.getWorkItem(),
repo, area, workItemClient, iAuditableClient);

if (getApiName() != null || getApiName().length() > 0) {
workingCopy.setWorkflowAction(getApiName());
}

IStatus status = workingCopy.save(monitor);

if (status.getSeverity() == IStatus.CANCEL || status.getSeverity() ==
IStatus.ERROR) {
throw new TeamRepositoryException(repo, status.getMessage(),
status.getException());
} else {
transaction.set(ConfigurationMapper.PARAM_CDERESOURCEKEY, new
Integer(workingCopy.getWorkItem().getId()));
}
} catch (TeamRepositoryException e) {
e.printStackTrace();
throw e;
} catch (Exception e) {
e.printStackTrace();
throw new TeamRepositoryException(e);
}
}


Output:

**********************4179
**********************update Driver6 prog guide
org.eclipse.core.runtime.AssertionFailedException: null argument:
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:84)
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:72)
at
com.ibm.team.workitem.client.WorkItemOperation.run(WorkItemOperation.java:91)
at
com.ibm.team.workitem.client.WorkItemOperation.run(WorkItemOperation.java:85)
at com.ibm.cde.jazz.actions.ActionCommon.execute(ActionCommon.java:110)
at com.ibm.cde.actions.AbstractAction.run(AbstractAction.java:250)
at
com.ibm.cde.bridge.ActionTransactionPair.run(ActionTransactionPair.java:167)


--
Sincerely,

Ahmed Hadad