Clear All notifications doesn't work anymore

Steps to reproduce:

1. Enable the Notification watch feature by changing the xwiki.properties file "notifications.watchedEntities.enabled = true"
2. Log in as a user that has notifications
3. Click on Clear All
4. Click on another page or refresh the page
5. Click on the Notifications list again

Expected results: All the notifications in the list are cleared.

Actual results: The notifications in the list are cleared but once the page is refreshed or the user clicks on another page, all notifications appear again.