java.lang.NullPointerException while generating new chunk; game crashes because of a superflat nether wastes world with ruined portals

I generated (wait, no, it crashed before I generated it) a superflat world with the following preset:

minecraft:bedrock,42*minecraft:dirt,minecraft:grass_block;minecraft:nether_wastes;ruined_portal

It's a world with a layer of bedrock, 42 layers of dirt, 1 layer of grass blocks, nether wastes biome and ruined portal generation. When I clicked "Create New World", the game crashed at 0% of world generation. Crash reports attached below.

NOTE: I did it twice to see if it happens every time and not just once so I will attach both reports.