I added the mod to ATM8 to play on a server with my friend however when i die the game crash (not the server) ,
you can see the error in the log file.

2023-09-23-4.log

I can attest this is an issue. https://gist.github.com/P3rf3ctXZer0/c969f3218194a8a4bb01b4822757d35f

This seems to be the offending line
[03.10 23:38:23] [Server] java.lang.NullPointerExceptionCannot invoke "online.kingdomkeys.kingdomkeys.capability.IPlayerCapabilities.getNumberOfAbilitiesEquipped(String)" because "playerData" is null