Comment 4 for bug 1398655

Hello, had a similar problem (Geary notification stuck there with no ability to clear). First you need to install dconf tools. Open a terminal window, type "sudo apt-get install dconf-tools" and press enter. Then run dconf editor from Applications. Navigate to the location com->canonical->indicator->messages and delete the value. You need to leave the brackets []. Exit the editor and restart OS, bell icon gone!