I have been trying to get Minecraft to run with a modpack that I am working on, I have eventually managed to get rid of the error message;
The game crashed whilst expection ticking world
Error: java.util.ConcurrentModificationException: null
Exit Code: -1
But as soon as that crash report stopped showing up, once the game crashed I would then get this error message instead;
The game crashed whilst ticking memory connectionError: java.util.ConcurrentModificationException: nullExit Code: -1
I just didnt know if this error message was due to a mod I had or if it was something to do with the base game itself.
In reply to smol_smeeep:
not from base game, that exit code of -1 usually suggests it is from modded.