[1.21.1] Stendhal crash with Connector Beta5 (possible version check issue?)

[VOLKOUL]

Mod Name

Stendhal

Mod Homepage

https://www.curseforge.com/minecraft/mc-mods/stendhal/files/all?page=1&pageSize=20

Minecraft version

1.21.1

Describe the bug

Crash on game launch. (Does not happen with Beta4)

Steps to reproduce

Install Connector, Extras, FFAPI & Stendhal.
Launch game.

Logs

Log: https://mclo.gs/JnhRBIx Crash: https://mclo.gs/D6IqaP4

Additional context

The Stendhal mod does not have an official 1.21.1 release.
The available 1.21 version worked without any issues (and without any edits to the META.INF files or fabric.mod) up to Beta5. The Stendhal mod contains an integrated library called lib.gui. As seen in the screenshot it is most likely the cause of the issue. I tried editing EVERY file mentioning the required MC version inside the integrated library and the mod itself, but it didn't seem to work. I am still getting the same crash.