FIX: notifications are missing under certain conditions

This simplifies the code for refreshing notification counts. It now
unconditionally looks up the user object which protects against stale objects
in memory.

This also removes a pile of conditional logic we no longer need.

app/models/notification.rb

@@ -217,15 +217,8 @@ class Notification < ActiveRecord::Base
   protected
 
   def refresh_notification_count
-    begin
-      if user.has_attribute?(:seen_notification_id)
-        user.notifications.reset
-        user.publish_notifications_state
-      else
-        User.find_by(id: user.id).publish_notifications_state
-      end
-    rescue ActiveRecord::RecordNotFound
-      # happens when we delete a user
+    if user_id
+      User.find_by(id: user_id)&.publish_notifications_state
     end
   end