Mobs can spawn on top of azaleas and flowering azaleas

Hostile mobs are able to spawn on top of azaleas and flowering azaleas.

To reproduce

1. Create a world
2. While in mid-air, type

   /fill ~10 ~ ~10 ~-10 ~ ~-10 minecraft:moss_block 

3. While standing on the moss block type

   /fill ~10 ~ ~10 ~-10 ~ ~-10 minecraft:flowering_azalea 

4. Set the time to midnight
5. Use

   /kill @e[type=!player] 

   → Mobs start to spawn on top of the azaleas