My game doesnt load, it crashes.

Put the summary of the bug you're having here

What I expected to happen was
Describe what you thought should happen here
Minecraft was gonna load.
What actually happened was...:
Describe what happened here
I clicked "start" and 5 seconds later the game crashes due to a bug.
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...