When ever i click on a world (and or multiplayer server world) it crashes

Put the summary of the bug you're having here

What I expected to happen was...:
I wanted to play normal Minecraft.

What actually happened was...:
When i click on a world (and or multiplayer world) it crashes

Steps to Reproduce:
1. I logged into Minecraft
2. ...I clicked on a single player world
3. ...It crashed