Error: java.lang.IllegalStateException: Missing: ResourceKey[minecraft:worldgen/biome / minecraft:plains]Exit Code: -1

I'm using the Caves & Cliffs resource pack.

I can create a new world and play on it with no trouble, but if I try to save it and then re-open it, the game crashes with the message Error: java.lang.IllegalStateException: Missing: ResourceKey[minecraft:worldgen/biome / minecraft:plains]
Exit Code: -1

This was happening in the previous snapshot as well, so it is not due to any changes made to the most recent snapshot.