The notification clean link should not navigate to an empty anchor

Steps to reproduce

• Log in on a site with a fixed top banner
• Make sure the current user has some notification alerts
• Head to a page with a table of contents and click one one of the named anchors in it
• Open up the notification alert menu
• Hit link "Clean all" (Note: it's not even needed to validate the confirmation modal, simply clicking on Clean All is enough to lose the context)

Actual result

• In the browser address bar, the URL fragment identifier gets updated to "#", which makes the window scroll up to the top and fire a popstate event (the navigation history gets updated)

Expected result

• Either the URL fragment identifier remains unchanged, or it gets modified only to reflect clearly the current page state