Whenever I join a minecraft server Minecraft crashes and it has a long page on the launcher

Put the summary of the bug you're having here

What I expected to happen was...:
I will join the server without any problems

What actually happened was...:
Minecraft crashed and had a long page of diffrent Sorce Files

Steps to Reproduce:
1. I just joined a server
2. Then it said logging in and showed the dirt screen before you join a server
3. Then it showed the page of Source Files