dispatch-operation: fix a race by waiting that TpCall is ready
dispatch-operation: fix a race by waiting that TpCall is ready

The call handler constructor rely on the TpCall to be ready (to fetch the
EmpathyContact associated with the call). If things are going fast (by
skipping the approving of the call and handling it right away for example) it
may no be ready yet.

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