Player can place top half slab under feet while standing on bottom half slab

Player can place top half slab under feet while standing on the bottom half slab. This should not be possible as the player is standing within the space the bock is to be placed. If the player is crouch walking while this bug occurs the player can fall off the edge of the block. A fairly minor bug but as you can see if you watch the attached video if this happens while bridging over the void the player will fall to his or her death which is how I came across this bug.

^{Edit by} @unknown

Steps to Reproduce:

• Place slab

• Stand on slab

• Place another slab on top of the first (at your feet)

• Notice player gets raised up