Put the summary of the bug you're having here

What I expected to happen was ...
Just switch back from a texture/resourcepack back to the default pack

What actually happened was...:
I clicked it. The Game shutted down, got this crash message. Restarted the game and the default minecraft was now chosen. If I switched back to the resourcepack it did what it should do.

Steps to Reproduce:
1. Download a resourcepack (like included as attachment)
2. Place it in the resourcepacks folder
3. Open the game and click on a resourcepack
4. Chose a resourcepack (like the included attachment)
5. When chosen click back on Default
6. The game shoot crash right now