Add sanity check and extra debug message

src/net/tcp.c

 		stop_timer ( &tcp->timer );
 		list_del ( &tcp->list );
 		ref_put ( &tcp->refcnt );
+		DBGC ( tcp, "TCP %p connection deleted\n", tcp );
 		return;
 	}
 
 static int tcp_open_uri ( struct xfer_interface *xfer, struct uri *uri ) {
 	struct sockaddr_tcpip peer;
 
+	/* Sanity check */
+	if ( ! uri->host )
+		return -EINVAL;
+
 	memset ( &peer, 0, sizeof ( peer ) );
 	peer.st_port = htons ( uri_port ( uri, 0 ) );
 	return xfer_open_named_socket ( xfer, SOCK_STREAM,