Grrr most common error people post about and no one ever seems to listen...
Null means not set to anything. It's like saying "open the door to my car" without telling you what car is mine. Go to line 2238 in packet handler and see what's there. It's not being set before it's used. breakpoint to try to debug and or just add better error checking (EG: if (objectVariableName == null) return

breakpointing is important though cause it could be something inside the object (most likely something inside client that is null.