empathy-chat: register the Handler when the app is activated
empathy-chat: register the Handler when the app is activated

This avoid to raise warnings when the app is launched a second time.

GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets