Lava/Water dripping particles spawn in mid air under half slab

Water/lava drops particles spawn in mid air under top half slab.

Steps to reproduce:
1. Launch any game (survival or creative)
2. Place halfslab on the ceiling (upper halfslab, cobblestone for example)
3. Place water or lava source on top of the half slab.
4. Observe the particles beneath the half slab spawning in mid air (see picture)