Prevent RTE being marked as dirty when content contains empty paragraph (#20335)

Prevent RTE being marked as dirty when content containt empty paragraph

In Tinymce, an empty paragraph is marked with a non-breaking space character.
When saving the content, the DOMParser replaces this empty non-breaking space character with an   entity.
This causes the editor to always be dirty when the content contains an empty paragraph.
By making these the same befor the comparison, this is prevented.

Author: mcl-sz

src/Umbraco.Web.UI.Client/src/common/services/tinymce.service.js

@@ -1465,7 +1465,8 @@ function tinyMceService($rootScope, $q, imageHelper, $locale, $http, $timeout, s
 
       function syncContent() {
 
-        const content = args.editor.getContent();
+        //get the content from tinyMCE and replace Non-breaking space character to HTML Entity
+        const content = args.editor.getContent().replace('\u00A0', ' ');
 
         if (getPropertyValue() === content) {
           return;