Well actually that's not the only way, I faced that problem with group chats, so what you can do instead of rebooting the phone, just open terminal, as normal user, type Code: top this will give you the top processes running on the N9 (then do ctrl + c to get out of top), look for the one that says wazap (the column on the right) and get its PID (first column on left) then just kill the process using its PID, for example Code: kill 8716 now you can start wazapp normally
top
kill 8716
killall wazapp