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.