Mod loader
Fabric

Minecraft version
1.20.1

Mod version:
1.1.3

Strange thing to have an incompatability with, but its about the only thing I can decypher from the error log:

As you can see there's a null method invoked, which may be on their end, not yours but I'll repost this issue on their repository as well.
(Edit, the same crash is on their repository already, I jumped the gun...)

Yeah as noted, this is on their side.