Fix for occasional crash due to data updating

Javaviz will randomly crash every once in a while, if data happens to get updated during this function.  I just followed the previous solution of ignoring the error, since we'll be getting plenty more data.
That would be a better solution, but I think it would be pretty complicated to get working (with the mix of java, python, servers, etc.).  And since it doesn't really matter if we drop one packet every once in a while (this error is quite rare), I think the slacker solution is OK.