Single view does not prompt to save changes

“Single view” changes don't warn if you leave without saving!!!

Edited to add steps to reproduce in 4.3:

1. Go to single view, select a student and turn edit mode on.
2. Click to override a grade then enter a grade and/or feedback.
3. Go elsewhere e.g. to the single view for another student.

Expected result: You are warned that you have changes which need saving.

Actual result: You leave the page without warning. If you return to the page, the grade and/or feedback previously entered is gone (because you didn't press the save button).