Objects inheriting from MiniObject are unrefing their native handle twice.

Gst.MiniObject implements the following finalizer:

	~MiniObject ()
		{
			if (!Owned)
				return;
			FinalizerInfo info = new FinalizerInfo (Handle);
			GLib.Timeout.Add (50, new GLib.TimeoutHandler (info.Handler));
		}

Gst.Message:Gst.MiniObject also implements a similar finalizer:

	~Message ()
		{
			if (!Owned)
				return;
			FinalizerInfo info = new FinalizerInfo (Handle);
			GLib.Timeout.Add (50, new GLib.TimeoutHandler (info.Handler));
		}

When the GC kicks in for a Gst.Message it will call both finalizers, ending with an extra unref.

see: https://github.com/GLibSharp/GtkSharp/issues/54