silent warning in GCC 7 (switch/case fallthrough)

miniupnpd/upnpevents.c

@@ -1,4 +1,4 @@
-/* $Id: upnpevents.c,v 1.42 2019/04/09 20:04:34 nanard Exp $ */
+/* $Id: upnpevents.c,v 1.43 2019/05/20 19:59:21 nanard Exp $ */
 /* vim: tabstop=4 shiftwidth=4 noexpandtab
  * MiniUPnP project
  * http://miniupnp.free.fr/ or http://miniupnp.tuxfamily.org/
@@ -583,6 +583,9 @@ void upnpevents_selectfds(fd_set *readset, fd_set *writeset, int * max_fd)
 				upnp_event_notify_connect(obj);
 				if(obj->state != EConnecting)
 					break;
+#if defined(__GNUC__) && (__GNUC__ >= 7)
+				__attribute__ ((fallthrough));
+#endif
 			case EConnecting:
 			case ESending:
 				FD_SET(obj->s, writeset);