Change the default return value of the ::message-received signal
Change the default return value of the ::message-received signal

If no signal handler has been connected to the ::message-received
signal, UniqueApp should return UNIQUE_RESPONSE_OK by default and
not UNIQUE_RESPONSE_INVALID.

Distrotech/libunique,GNOME/unique,Distrotech/libunique,GNOME/unique,Distrotech/libunique,GNOME/unique