Hey! Thee is a crash log with Classy Hats 1.5.

I tried to test Classy Hats mod with my Metamorph mod (in order to make sure that the hats are show up on the head), and I couldn't open the Hat Inventory. Every time I pressed the button, the same exact exception was thrown as in the crash log. Then I looked up the tooltip and tried to put the hat on using sneak + right click, and boom, it crashed.

I'll try testing with Classy Hats 1.4, a bit later.