Change Details

Tested in combination with later diffs, to confirm that it's possible for some message types to not set a thread to unread

* Tested creating a sidebar from a non-viewer message with a multimedia message, and confirmed it only sent 1 notif to the other user in the sidebar (the author of the sidebar source message) * Tested sending a normal multimedia and confirmed that it still sent a notif

* Tested in combinationcreating a sidebar from a non-viewer message with later diffsa multimedia message, to confirm that it's possible for some message types to not set a thread to unreadand confirmed it only sent 1 notif to the other user in the sidebar (the author of the sidebar source message) * Tested sending a normal multimedia and confirmed that it still sent a notif