Armor Stand disappears after 2 slabs were placed

What I expected to happen was...:
Nothing should've happened to the armor stand

What actually happened was...:
Disappeared after leaving the spot including what was in the slab. In this case, a cake slice

Steps to Reproduce:
1. Get an armor stand
2. Put armor on stand
3. Place slabs next to armor stand
4. Leave the spot
5. Return
6. Notice that the slab(s) and armor stand is missing