Wall Planter Should Be Blocked From Placement When Behind Plant Life

I would call this more of an oversight than a bug, but a Wall Planter when placed needs to also check the foreground layer to see if a plant already exists in that space.

I planted the Wall Planter two tiles higher than the Clam thinking it had the same height as the Coral and not three. I got confused why I couldn't place a Starfish even though I could place the Wall Planter.