Summary:
Sculk vein sometimes generate floating inside mineshaft. This generation happens if the mine is generated in the Deep Dark biome. Sculk vein can be generated completely without any support block.

Seed: 8596880061270485395
Coords: 1475 -49 -2082
Coords: 1491 -50 -2090

Steps to reproduce:

1. Create a world with the specified seed.
2. Visit the specified coordinates.

Observed results:
Sculk vein generate floating inside mineshaft.

Expected results:
Sculk vein will only generate on blocks, not in the air.

Image: