Modloader
Fabric 1.17.1
Describe the bug
When trying to talk to the Guild Master, the client fails

To Reproduce
Steps to reproduce the behavior:

1. I find the Guild Master
2. I click on it with the right mouse button
3. A crash occurs
   crash-2021-09-20_10.29.24-client.txt

Hello Anhelm.
I've added some extra checks to avoid that crash.
There's the possibility that the Guild Master is selling an invalid profession licence (damn those villagers!).
The changes on version 0.0.6 should fix your problem, so I'm closing the issue for now.
If even with the v0.0.6 you still experience the problem please open a new issue with the updated error log.
Thank you!