When attempting to close a world with the latest version (2.0.6) Minecraft crashes... after the world has closed.

Open a world
Close the world

Booted to main menu as expected when you close a world.

Not sure what to put here

I'm not good at reading crash reports, but it might have something to do with the mod trying to clear a skin data pool?
crashreport.txt

@Swirtzly Why would anyone ever want to throw an IllegalStateException without a message