One more tiny window pulling fix

Created by: Exxion

There's still a rather obscure circumstance in which pulling a window will fail when it shouldn't. I was going to fix it in #4040, but then I fell asleep and that got merged. Basically, pulling a window diagonally around a corner against a wall while the window was facing a certain direction would fail. This fixes that by adding a check for border objects to the Adjacent() diagonal case similar to the one added to the non-diagonal case in #4040. There was another case I expected it to fail in after looking over the change, but I tested it and it didn't fail. Not totally sure why, but I'm not complaining.