tileseditor: Don't allow tiles to move tiles already at minimum size

Previously a tile could intersect with the tile next to it when resizing tiles in tiles-editor.

This checks that the tile next to the resized one is not at minimum size already, and stops resizing if it is.

Do note that any current setups that may get broken if there is tiles that intersect each other, so they may have to remake the tile setup.

BUG: 465721 FIXED-IN: 6.0.1