MINECRAFT KEEPS CRASHING 1.8.9

Put the summary of the bug you're having here
It just keeps crashing whenever I try to open a world

What I expected to happen was...:
Describe what you thought should happen here
if I opened minecraft again that it wouldn't crash again

What actually happened was...:
Describe what happened here
kept crashing over 5 times

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...

not sure