proto-standard/msg: keep len if pack_announce hook returned 0

Signed-off-by: Adam Wujek <dev_public@wujek.eu>

proto-standard/msg.c

@@ -214,6 +214,7 @@ static int msg_pack_announce(struct pp_instance *ppi)
 	UInteger8 *flags8 = buf + 6;;
 	const struct pp_msgtype_info *mf = pp_msgtype_info + PPM_ANNOUNCE_FMT;
 	int len= __msg_pack_header(ppi, mf);
+	int ret = 0;
 
 	/* Header */
 	__msg_set_seq_id(ppi,mf);
@@ -236,7 +237,9 @@ static int msg_pack_announce(struct pp_instance *ppi)
 	*(Enumeration8 *) (buf + 63) = DSPRO(ppi)->timeSource;
 
 	if (is_ext_hook_available(ppi,pack_announce))
-		len = ppi->ext_hooks->pack_announce(ppi);
+		ret = ppi->ext_hooks->pack_announce(ppi);
+	if (ret)
+		len = ret;
 	return len;
 }