gstreamer-buffer: Make the stage color fully opaque

Using an alpha value of 0 makes the stage transparent if the device
happens to have an ARGB visual on X (or always on wayland)

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Philip Withnall <philip.withnall@collabora.co.uk>
Reviewed-by: Mathieu Duponchelle <meh@collabora.co.uk>

Differential Revision: https://phabricator.apertis.org/D1154

gstreamer-buffering/automated/video-player.c

@@ -501,7 +501,7 @@ main (int argc, char *argv[])
   GstElement          *goomsource;
   GstIterator         *iter;
   ClutterActor        *stage;
-  ClutterColor         stage_color = { 0x00, 0x00, 0x00, 0x00 };
+  ClutterColor         stage_color = { 0x00, 0x00, 0x00, 0xff };
   ClutterColor         control_color1 = { 73, 74, 77, 0xee };
   ClutterColor         control_color2 = { 0xcc, 0xcc, 0xcc, 0xff };
   GError              *error = NULL;