Plants float upon being exploded while in a snow layer

Plants placed in a snow layer do not break from explosions from TNT and creepers.

Steps to reproduce

1. Place any plant that can be placed in the same block with the snow layer (flowers, grass)
2. Place a snow layer in the same space as the plant
3. Place a creeper or TNT next to it
4. Explode the creeper or TNT

Observed results

All blocks around the plant are destroyed; the plant is left floating in the air.

Expected results

The plant, like the rest of the blocks, will be destroyed by the explosion.