Game crash due to exception in server tick loop

[FallenAngel]

So I made a modpack a few years ago as my own rendition of CrazyCraft, but modern (at the time, which was 1.12.2) and bigger. The pack loads just fine and I can do things in the main menu, but whenever I try to load a new world (fresh modpack, no old saves) it gets to "Loading Terrain" and then crashes. Giving me the crash report of "The game crashed whilst exception in server tick loop. Error: Java.lang.ArrayIndexOutOfBoundsException. Exit Code: -1"

What's going on, and how do I fix this? I really need the pack to work, as this is a rebuild of the original pack I made from 3 years ago and I need to get it published because people want to play it due to Ssundee's new minecraft series InsaneCraft (my modpack name is Super InsaneCraft)

Linked below is the full crash report. Please someone help me fix this

crash-2021-06-02_02.42.23-server.txtFetching info...

[DaemonUmbra]

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.