Archive conversation follow ups #2

[mahibi]

1. After filtering for archived conversations and forgetting about it, i was shocked for some seconds why the conversations don't load. Turned out i had the filter enabled but no conv is archived. In this case we should give a hint about it as a text in middle of the screen.
   Please check how it's done on iOS.

2. the "Unread mentions" bubble is not updated when filtering