Bad bug

Put the summary of the bug you're having here
Well i couldn't join 1.7 servers it just crashed my game.
What I expected to happen was...:
Describe what you thought should happen here
I thought that i could join 1.7 servers without crashing with restarting pc and minecraft.
What actually happened was...:
Describe what happened here
When i tried to join 1.7 servers it crashed my game.
Steps to Reproduce:
1. I went on a server downloaded optifine
2. I went off 1.8.1 in 1.7 and went on a server
3. I couldn't join servers 1.7 it just keeps crashing my game. I deleted optifine still does it.