Metadata changed mail notification endless loop

Some users get a metadata changed notification every 15 Minutes.

Reason
The user had a follower who is now deactivated or removed in the external user directory. Metadata does not correctly null check these following users.

Workaround 1 - temporarily deactivate the metadata mail job

1. Go to the Addon Manager in your Confluence Administration
2. Klick on the "Metadata for Confluence" Addon Entry
3. Open the modules of this addon via the little plus icon
4. Deactivate the following modules
   1. Mail Notification Job (metadataMailNotificationJob)
   2. Mail Notificaiton Job Trigger

Workaround 1 - mail reciever page unfollow
The mail reciever can simply remove himself from the page watch list