On my server list, the server that I was attempting to join was us.shotbow.net. Before the client was done polling the server to see that it was outdated, it allowed me to press the join server button. An easy way to fix this is to disable the join server button while the game is polling a server.

What I expected to happen was...:
The game would not let me connect to the server because it was still running 1.5.2.

What actually happened was...:
It let me connect to the server even though I am using 1.6.1. It then crashed with the attached crash report.

Steps to Reproduce:
1. Add a server to your server list that is still running 1.5.2
2. Either refresh the server list until it says Communication Error or join the server while it is still polling
3. Your game will crash with the attached crash report