Game crashes when joining a server

Put the summary of the bug you're having here

What I expected to happen was...:
that I would join a server without crashing.

What actually happened was...:
When I selected a multiplayer server to join, instead of joining, it crashed as soon as "Join Server" was clicked. Same thing happens with single player.

Steps to Reproduce:
1. Select version 1.7.10
2. Join Multiplayer or Singleplayer server
3. Watch as the game crashes