GtkGst unref error

public static void main (string[] args) {
        X.init_threads();
        Gst.init (ref args);
        Gtk.init (ref args);

        var sink = Gst.ElementFactory.make ("gtksink", "sink");
        var playbin = Gst.ElementFactory.make ("playbin", "bin");
        playbin["video-sink"] = sink;
        playbin["uri"] = "http://hd2.lagrosseradio.info:8200";
        Gtk.Widget area;
        sink.get ("widget", out area);
        var win = new Gtk.Window();
        var bar = new Gtk.HeaderBar();
        bar.title = "Test";
        bar.show_close_button = true;
        win.set_titlebar (bar);
        win.add (area);
        win.realize.connect (() => {
                playbin.set_state (Gst.State.PLAYING);
        });
        win.set_size_request (400, 300);
        win.show_all();
        Gtk.main();
}