Nylium does not decay into netherrack when a snow layer is placed on top of it

Summary:
When a snow layer is placed on top of nylium, the nylium does not decay into netherrack over time.

Steps to Reproduce:

1. Find a snow biome (so that the snow layer does not melt)
2. Place a block of nylium
3. Place a snow layer on top of it
4. Wait a few minutes or increase the randomtickspeed

Observed Results:
The nylium does not decay into netherrack.

Expected Results:
The nylium should decay into netherrack.