When I press play on the loadscreen it crashes

Put the summary of the bug you're having here
When I press play on the loadscreen it crashes
What I expected to happen was...:
That minecraft would've had bring me to the titlescreen

What actually happened was...:
It didn't bring me to the titelscreen and showed me that is crashed

Steps to Reproduce:
1. start minecraft
2. load your profile
3. press play
4. it crashes