Crashing

Put the summary of the bug you're having here

What I expected to happen was that i got a head, because i was on a webside that said how to get heads with a picture, and i tested the command and i wrote lol on the place i was supposed to put the exact image file

What actually happened was that minecraft now crashes everytime i go on the server this was on (the ip is mc.pineapplecraft.org)

Steps to Reproduce:
I have no idea how to fix this