i dont understand this 1.6.73-j issue please help

Put the summary of the bug you're having here:
It not letting me get on mineshafter
*What I expected to happen was:
that i open up the ms but no it made me crash
Describe what you thought should happen here:
That someone can fix this so i can get on

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. 1st i open up the launcher
3. 2nd i click to open it
4. It made me crash