[empathy] Fix crash on hangup with no video

[Guillaume Desmottes <gdesmott src gnome org>]

commit 7b12eea87d880aa47f7fac77c1a0c0c23cd91330
Author: Emanuele Aina <emanuele aina collabora com>
Date:   Wed Mar 14 17:00:10 2012 +0100

    Fix crash on hangup with no video
    
    Insufficient refcount on priv->video_preview_sink caused segfaults
    when accessing freed data.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=672063

 src/empathy-call-window.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/src/empathy-call-window.c b/src/empathy-call-window.c
index 565b9ed..10333d6 100644
--- a/src/empathy-call-window.c
+++ b/src/empathy-call-window.c
@@ -1082,9 +1082,9 @@ create_video_preview (EmpathyCallWindow *self)
 
   priv->video_preview_sink = gst_element_factory_make ("cluttersink", NULL);
   if (priv->video_preview_sink == NULL)
-    g_error ("Missing cluttersink");
-  else
-    g_object_set (priv->video_preview_sink, "texture", preview, NULL);
+      g_error ("Missing cluttersink, check your clutter-gst installation");
+  g_object_set (priv->video_preview_sink, "texture", preview, NULL);
+  g_object_add_weak_pointer (G_OBJECT (priv->video_preview_sink), (gpointer) &priv->video_preview_sink);
 
   /* Add a little offset to the video preview */
   layout = clutter_bin_layout_new (CLUTTER_BIN_ALIGNMENT_CENTER,
@@ -3626,7 +3626,8 @@ empathy_call_window_bus_message (GstBus *bus, GstMessage *message,
                   start_call (self);
               }
           }
-        if (GST_MESSAGE_SRC (message) == GST_OBJECT (priv->video_preview_sink))
+        if (priv->video_preview_sink != NULL &&
+            GST_MESSAGE_SRC (message) == GST_OBJECT (priv->video_preview_sink))
           {
             gst_message_parse_state_changed (message, NULL, &newstate,
                 &pending);