Bug: Notifications should handle deleted posts better
If a member accrues some notifications about a post, and then the post gets deleted, when the member clicks through from the notification to see the post, they receive an error message "Sequence contains no elements".
The error message needs to be more descriptive about what has happened.
It would also be an improvement if notifications were deleted or replaced by a "post was deleted" notification when the post they refer to is deleted. (An error message when clicking through to the post is still required, even if the notifications get deleted, because members could have outdated local copies of notifications in their browser while they are logged in.)