Game crashes when creating a superflat world with unknown biome

When you put an unknown biome in superflat it should reset but it saves and when you press done or presets it crashes.

Steps to reproduce:

1. create new world
2. pake it superflat
3. press customize
4. press presets
5. type a biome that doesnt exist replacing "minecraft:plains"
6. press done
7. press presets or done