It crashing when i join my server:( PLEASE help!

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What I expected to happen was....
Describe what you thought should happen here
What I expected to happen was to start playing normaly on my server...
What actually happened was...:
Describe what happened here
What actually happened was that my minecraft crashed...

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...