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...:
Describe what you thought should happen here
I will join the server without any problems
What actually happened was...:
Describe what happened here
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