Biome placement by depth fails on Neoforge 1.21.1 down near the bottom of the world

[gniftygnome]

In Neoforge 1.21.1 roughly between depth 0.8 and 1, it's been reported biome placement based on depth fails and Biolith's describe command returns an error. I need to develop a reproduction and then suss out what is going on. Maybe also check Fabric to see if this is a vanilla thing or if I need to go read neo patches.

[gniftygnome]

The error in question was caused by a logic error in the special code used to handle the describe command. In places where a replacement biome was selected and the original biome had sub-biome requests, but the selected replacement had no sub-biome requests, there was a missing HashMap.contains(Object) guard resulting in an attempt to dereference null. This will be fixed in the next releases.

Placement (or not) of biomes uses different, faster code (because it has better access to biome placement internals and does not need to report on intermediate results), so that part of this bug report would be another matter I still need to make a test for.