fix WELCOME deserialization: skip atl+adm_tags_sig fields before address data

src/chat/chat_sync.c

@@ -1162,6 +1162,10 @@ static void cs_handle_welcome(struct chat_sync* cs, uint64_t peer,
         char peer_userinfo[256] = "";
         if (nl && p + nl <= pl + len) { memcpy(peer_userinfo, p, nl); peer_userinfo[nl] = '\0'; p += nl; }
         uint8_t ac = *p++;
+        uint8_t atl = *p++;
+        if (atl > 0 && p + atl <= pl + len) p += atl;
+        p += 64; /* adm_tags_sig */
+
 
         /* verify join_sig if present */
         if (join_sig) {