ProcessInstance tasks break if assignee requested is not part of a group

[fitzpatrick]

/cow-server-new/processInstances/tasks?assignee=username

This returns an exception if the username is not part of any groups.

SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/cow-server-new] threw exception [Request processing failed; nested exception is java.lang.RuntimeException: Server-side Exception: Command QueryTasksAssignedAsPotentialOwner faild due to Operation failed. Please contact task server administrator.] with root cause
java.lang.RuntimeException: Server-side Exception: Command QueryTasksAssignedAsPotentialOwner faild due to Operation failed. Please contact task server administrator.
at sun.reflect.GeneratedConstructorAccessor387.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at org.jbpm.task.service.responsehandlers.AbstractBaseResponseHandler.createSideException(AbstractBaseResponseHandler.java:73)
at org.jbpm.task.service.responsehandlers.AbstractBlockingResponseHandler.waitTillDone(AbstractBlockingResponseHandler.java:48)
at org.jbpm.task.service.responsehandlers.BlockingTaskSummaryResponseHandler.getResults(BlockingTaskSummaryResponseHandler.java:38)
at org.wiredwidgets.cow.server.service.TaskServiceImpl.findPersonalTasks(TaskServiceImpl.java:84)
at sun.reflect.GeneratedMethodAccessor134.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)