Hi, today my players were messing around and the server went down after one of them activated a Dispenser holding some Player Heads (not custom heads, if that matters). Unfortunately I have no idea what log file it's in, but here's the crash:

https://pastebin.com/2bqnU6ty

Forge: 43.2.8
Quark: 3.4-405
AutoRegLib: 1.8.2-55

fixed!