Whenever I open my worlds, it crashes. I really like these worlds, I have worked very hard on 1 of them and do not want to lose it.

Put the summary of the bug you're having here

What I expected to happen was when I opened the world, it would load in.
Describe what you thought should happen here

What actually happened was, the game crashed.
Describe what happened here

Steps to Reproduce:
1. Open Minecraft
2. Select "Single Player"
3. Select world, and hit "Play Selected World"