[cogl/cogl-1.18] cogl-gst: Fix get_caps implementation when no context is set

[Neil Roberts <nroberts src gnome org>]

commit b898333181e284164516e7171a14c5ca04773dd5
Author: Neil Roberts <neil linux intel com>
Date:   Tue Jan 21 17:33:57 2014 +0000

    cogl-gst: Fix get_caps implementation when no context is set
    
    If no context is set on the CoglGstVideoSink then it would previously
    call gst_caps_ref with a NULL pointer. This patch makes it just return
    NULL instead. I think that is a valid thing to do because that is what
    gst_base_sink_default_get_caps does. If we don't do this then it's not
    possible to use CoglGstVideoSink with GstParse because that tries to
    link the pipeline after parsing the string. That was previously
    causing a critical error because the freshly parsed sink doesn't have
    a CoglContext.
    
    Reviewed-by: Robert Bragg <robert linux intel com>
    Reviewed-by: Lionel Landwerlin <llandwerlin gmail com>
    (cherry picked from commit cf26da2964e372c9fe5bd6da060a57006a83af38)

 cogl-gst/cogl-gst-video-sink.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/cogl-gst/cogl-gst-video-sink.c b/cogl-gst/cogl-gst-video-sink.c
index 7e89636..31891ea 100644
--- a/cogl-gst/cogl-gst-video-sink.c
+++ b/cogl-gst/cogl-gst-video-sink.c
@@ -1126,7 +1126,11 @@ cogl_gst_video_sink_get_caps (GstBaseSink *bsink,
 {
   CoglGstVideoSink *sink;
   sink = COGL_GST_VIDEO_SINK (bsink);
-  return gst_caps_ref (sink->priv->caps);
+
+  if (sink->priv->caps == NULL)
+    return NULL;
+  else
+    return gst_caps_ref (sink->priv->caps);
 }
 
 static CoglBool