Reproducing:
- Open the editor.
- Try to mousewheel zoom by while the mouse itself is outside the level boundaries on the bottom or right side (left and top outside boundaries seem to be ok).
Note: This has to be the first mousewheel zoom you do since opening the editor. When you had 1 successful zoom before, the error doesn't occur anymore.
- Get a nice error message that implies the program tried to devide by zero. All future zooms will cause the same error now.
Weirdly enough, this is exactly the same debugging statement that cause the exception on changing the level size.