Door Bug Smashing top half gives nothing, but smashing bottom half gives two doors.

Put the summary of the bug you're having here

What I expected to happen was...:
For the door to just break.

What actually happened was:
Smashing top half gave nothing of the door, but smashing the bottom half gave two doors, so basically another duplication

Steps to Reproduce:
1. Place a door in survival
2. Destroy the top half, gives nothing
3. Then place abother door down, and smash the bottom half for two doors.