Attempted starting the game, and it crashed.

Put the summary of the bug you're having here

What I expected to happen was...:
The game to open up and start.

What actually happened was...:
It would start loading, then return to the launcher, before finally crashing.

Steps to Reproduce:
1. Open Launcher
2. Click Play
3. Select World
4. Wait for Load
5. Start from number 2 again.