SlashBlade version: SlashBlade-mc1.12-r26
Forge version: 1.12.2 - 14.23.5.2838
How to reproduce crash:

1. get an used slashblade;
2. craft it and some materials to mend it, and materials should be more than the slashblade's durability loss.
3. game crashes.
   Here's a GIF:
   
   Crash report:
   https://paste.dimdev.org/ximedofije.mccrash

#83