minecraft 1.7.2 crash on servers

Put the summary of the bug you're having here

What I expected to happen was...:that I normally start minecraft but it was the opposite

What actually happened was...:does not match my minecraft through 1.7.2 - 1.7.9 So just when I want to go to the server, the game crashes

Steps to Reproduce:
1.I've been turned minecraft 1.7.2
2.I went to the server
3.game I fell