With the 5.0.1.3 update of the mod loading or creating a world results in a crash.
Crash Log: https://gist.github.com/Wxrlds/bd7212e525e4e8aeefc61b2d77d5ccab

I'm having the same problem, actually!

I know it's been some time, but if you still have the problem try the latest version https://www.curseforge.com/minecraft/mc-mods/global-gamerules/files/3378657