Server crash 1.12.2

It seems like a mod is registering a new biome type, however not including an ID for the biome. If this is the case then the mod registering the biome is doing something that shouldnt be done.

Have you got a log of the server booting? I think Forge points out mods that register something without a valid/dangerous id. If you know the mod then you can tell the developer the issue and they should be able to fix it