video-texture: set_uri (NULL) now goes to "idle" mode and stops playing
video-texture: set_uri (NULL) now goes to "idle" mode and stops playing

set_uri (NULL) was given directly to playbin2 (which was pretting a
debug message btw). We now intercept NULL in set_uri: it stops the
current video and goes to "idle" mode (ie next paint will use the
idle material).

skinkie/clutter-gst,skinkie/clutter-gst,GNOME/clutter-gst,lubosz/clutter-gst,GNOME/clutter-gst,lubosz/clutter-gst,skinkie/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst