Structure void replaced by falling snow layer

Problem:
when a layer of snow falls into a structure void, it will replace the structure void instead of being destroyed.

How to reproduce:
1.place three blocks as below:

3 snow layer
2 any block
1 structure void
0 (ground)

2.destroy the block on layer 2, and you'll see this:

falling snow layer

1 structure void
0 (ground)

then:

1 snow layer
0 (gorund)

Result:
the structure void has been replaced.

Expected:
the snow layer is destroyed.