Mouse pointer does not reflect if drag-and-drop will move or copy

1. Open two empty editor splits.
2. Open a file in one of these splits.
3. Drag the file to the other split.
   It will be moved to the other split.
4. Drag the file to the other split while pressing Ctrl.
   It will be copied to the other split.
5. Now look closely at the mouse pointer during steps 3 and 4.
   In both cases, it has a small "move" arrow:

The mouse pointer should have a "Plus" sign while Ctrl is being pressed.