bin: Use allow-none instead of nullable until we depend on a new enough GI version
bin: Use allow-none instead of nullable until we depend on a new enough GI version

surround-io/gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,surround-io/gstreamer,surround-io/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,jpakkane/gstreamer