I you inadvertently close the program, you will be prompted if there is
unsaved data: save changes Yes / no , but there is no abort button.

The reason I have not flagged this as trivial or enhancement is that the
default option is NOT to save the changes, so if you are not paying too
much attention to the message in the dialog (perhaps you had intended to
close a different program or window) and simply get rid of the dialog by
pressing 'x' in the title bar or ESC then you lose all your work (as I have
done several times).

Of course, defaulting to saving changes may also cause some people a lot of
grief, so the safest tactic is to provide an 'abort' (cancel) option and
default to that.