The issue can be easily reproduced by submitting a query that throws an exception with a null message, e.g.
:> throw new RuntimeException()
This results in a NPE on the client end in GryoMessageSerializerV1d0.dese
The offending code is the invocation of .intern() on statusMsg on line 208
There are several ways to fix this problem, but I don't see the utility behind interning the message so I suggest removing the call to intern.