Since i've change a ressource pack, the laucher crash when the Mojang window appears.

Put the summary of the bug you're having here

What I expected to happen was...:
I wished to change the ressource pack

What actually happened was...:
Since i've change a ressource pack, the laucher crash when the Mojang window appears.

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