Fix cursor in editor

I noticed that when editing a map and the cursor is set to a tile, it doesn't change back to an arrow when hovering over the GUI. I made it do that.
There's a small problem in the way I implemented it: you must always have a tile selected, which means that right click doesn't change back to arrow cursor anymore. I don't know how to fix this, since I can't find an event for right click. Please let me know what you want me to do about this.