'Stop Watching' does not work for Pages from Spaces the user no longer has permissions

Issue Summary

If a user no longer has permissions to a Space, he cannot stop watching specific pages from that space, as the link in the Watches pages does not work.

Steps to Reproduce

1. Using an Admin account, create new space and a Page called "Sample" within the space;
   • Ensure the User account has View permissions on the new Space;
2. Logout and login with the User account;
3. Open the "Sample" page from new space and click on Watch > Watch page;
4. Logout and login with the Admin account;
5. Open the new space Permissions page and remove permissions for the User;
6. Logout and login with the User account;
7. Click on the profile picture . Watches;
8. The "Sample" page is listed in the Page Watches section
9. Click on Stop Watching
   • Link becomes Start Watching
10. Refresh the page
    • Link reverts back to Stop Watching

Expected Results

The page should be removed from the list when clicking Stop Watching. Optionally the Page watch should be removed when removing the User's space permission (this is what happens to the Space watch).

Actual Results

The page watch is not removed when removing the User's space permissions nor when clicking Stop Watching.

Workaround

A Space admin can remove the user's page watch via the Manage Watchers dialog.