Slideshow Edit screen Save warning

When you open a Slideshow and select Edit slideshow, you can reorder, add, insert, etc. then hit OK. It appears that you have saved the Slideshow (absolutely no other indication that there are unsaved changed), but you have not saved anything until you hit File -> Save. If you close the document you lose changes.

A warning that you are about to leave without saving changes would be great so that work is not lost.