There is an edge case where the following occurs:
1. The user sets a bookmark reminder on a post/topic
2. The post/topic is changed to a PM before or after the reminder
fires, and the notification remains unread by the user
3. The user opens their bookmark reminder notification list
and they can still see the notification even though they cannot
access the topic anymore
There is a very low chance for information leaking here, since
the only thing that could be exposed is the topic title if it
changes to something sensitive.
This commit filters the bookmark unread notifications by using
the bookmarkable can_see? methods and also prevents sending
reminder notifications for bookmarks the user can no longer see.
3c5fb871c0