Fix memory leak in appsrc example
Fix memory leak in appsrc example

freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,GStreamer/gstreamer-sharp,Forage/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,GStreamer/gstreamer-sharp,Forage/gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,Forage/gstreamer-sharp,GStreamer/gstreamer-sharp,Forage/gstreamer-sharp