Crashes when I hit play, but sometimes if I do get in the game, if I change resource pack EVERYTHING turns pink and black, then when I try to change back, it crashes.

Put the summary of the bug you're having here

What I expected to happen was...:
When I hit play, I play. And if I get in, when I change resource pack, it works, and if I return to default it does.

What actually happened was...:
Sometimes when I hit play on the launcher, it instantly crashes. If I change resource pack (The pack is NOT the problem), EVERYTHING turns pink/black except a few blocks, but it still says the default texture pack is selected, and if I'm fast enough I can get in a world, but it crashes.

Steps to Reproduce:
1. Hit play
OR
2. Change Resource Pack
OR
3. Join/Create a world