Door duplication bug, easy to recreate and should be fixed

How-to:

1. Place a redstone 1 block above the grond (against the wall)
2. Place a door on the ground below the torch
3. Get 2 doors back

This works with both wooden and iron doors.
If it is still unclear to you, here is a gif:
http://giant.gfycat.com/DifferentSarcasticArmedcrab.gif