If placing a block next to fences/iron bars with an entity at the space will create "ghost"

If you place a block next to fences/iron bars with an entity at that block, the placed block will disappear but the fence/iron bar will still be connected to that "block"

 

Steps to Reproduce:

1. Make a villager stand on a Stonecutter.

2. Place fences/iron bars around its head

3. Place a block right above its head