it crashes when it is done loading it worked yesterday

Put the summary of the bug you're having here

What I expected to happen was...: 
Describe what you thought should happen here  it to put me to main menue

What actually happened was...:
Describe what happened here it says this The game crashed whilst initializing game

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ... playing minecraft 
3. ... on windows 10