open any Minecraft world and crash

Put the summary of the bug you're having here
if i open any minecraft world it will instantly crash!
What I expected to happen was...:
Describe what you thought should happen here
the world should load and not crash my game!
What actually happened was...:
Describe what happened here
the game crashed every time i opened a world
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ... open world and wait for it to load
3. ...then it crashes!!!!