Fix hasNoChanges description comparison (#244521)

## Summary

This PR fixes a bug where for dashboard listing page, some recent change
made it so a newly created dashboard has description as `undefined`
instead of an empty string, this leads to the content editor flyout
always showing as having changes as the description comparison check
wouldn't work properly.

(cherry picked from commit 2cb23e1)

Author: kowalczyk-krzysztof

src/platform/packages/shared/content-management/content_editor/src/components/editor_flyout_content.tsx

@@ -88,9 +88,11 @@ export const ContentEditorFlyoutContent: FC<Props> = ({
       return arr1.every((tag: string, index) => tag === arr2[index]);
     };
 
+    const description = item.description || '';
+
     return (
       item.title === form.title.value &&
-      item.description === form.description.value &&
+      description === form.description.value &&
       compareTags(itemTags, formTags)
     );
   };