check state of the context when accepting/failing/delaying
check state of the context when accepting/failing/delaying

Also set dbus_context to NULL once we return as it's freed by dbus-glib.

Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib