If you have tapped the X to clear the filters at the far right side and nothing happens, that means you have songs in your database with a blank title. This is very unusual, and I'm not sure how you ended up in that state (unless you imported a CSV with blank titles for some of the songs or something of that sort). MobileSheets normally would not allow songs to be created with a blank title. Those song titles will have to be removed from the database manually. I can walk you through sending me the database file if you want to go down that path.
Mike
Mike