I have already seen this bug all over and have solved it. When switching from 1.8 to 1.7, often people leave the render distance on 32 chunks (not in 1.7). You simply need to change render distance in 1.7. Otherwise, the game will crash.

What I expected to happen was Minecraft to run normally.

What actually happened was the game crashed.

1. Leave 1.8 with 32 chunk render distance.
2. Go to 1.7
3. Don't change render distance.