The current GstURIHandlerInterface is:

[CCode (cheader_filename = "gst/gst.h", type_cname = "GstURIHandlerInterface", type_id = "gst_uri_handler_get_type ()")]
	public interface URIHandler : GLib.Object {
		[CCode (array_length = false, array_null_terminated = true)]
		public unowned string[] get_protocols ();
		public abstract string get_uri ();
		public Gst.URIType get_uri_type ();
		public abstract bool set_uri (string uri) throws GLib.Error;
	}

I believe the correct one should be:

[CCode (cheader_filename = "gst/gst.h", type_cname = "GstURIHandlerInterface", type_id = "gst_uri_handler_get_type ()")]
	public interface URIHandler : GLib.Object {
		[CCode (array_length = false, array_null_terminated = true)]
		public abstract unowned string[] get_protocols (GLib.Type type);
		public abstract string get_uri ();
                [CCode (vfunc_name = "get_type")]
		public abstract Gst.URIType get_uri_type (GLib.Type type);
		public abstract bool set_uri (string uri) throws GLib.Error;
	}