Prevent untiling window if it can't be tiled more in the same direction
Currently, if you press Meta+Up several times and there is no output higher, you are going to see the following:
- on the first Meta+Up, the window will be tiled so it occupies the top half of the screen
- on the second Meta+Up, the window will be untiled
This behavior is unexpected, and it looks confusing when you have a window that's tiled in the top left screen quadrant and press Meta+Up.