CallWindow: check the video exists before showing it
CallWindow: check the video exists before showing it

Since empathy_call_window_show_video_output_cb() is called
in an idle thread, it's possible that the video is removed
before the function is executed, so check if it's still there
before showing it.

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