Work Queue Screens - Selecting row that was already processed

When a work queue entry is processed, it is usually removed from the queue. If user has work queue screen opened and it contains “snapshot” of the data containing such entry (that is not already in the database) "Object reference not set to an instance of an object." is returned by the server. The failing request is MasterRecord.

The correct response should 404 and the client should inform user about the fact that the record is now longer available.