fix unnecessary popups about leaving the page

src/public/javascripts/services/note_detail.js

@@ -234,7 +234,7 @@ $(document).ready(() => {
 
 // this makes sure that when user e.g. reloads the page or navigates away from the page, the note's content is saved
 // this sends the request asynchronously and doesn't wait for result
-$(window).on('beforeunload', saveNoteIfChanged);
+$(window).on('beforeunload', () => { saveNoteIfChanged(); }); // don't convert to short form, handler doesn't like returned promise
 
 setInterval(saveNoteIfChanged, 5000);