Improve error message.

telegram-bot-api/Client.cpp

@@ -12119,7 +12119,7 @@ void Client::on_message_send_failed(int64 chat_id, int64 old_message_id, int64 n
   auto &query = *pending_send_message_queries_[query_id];
   if (query.is_multisend) {
     if (query.error == nullptr || query.error->message_ == "Group send failed") {
-      if (is_special_error_code(error->code_) || error->message_ == "Group send failed") {
+      if (is_special_error_code(error->code_) || error->code_ == 406 || error->message_ == "Group send failed") {
         query.error = std::move(error);
       } else {
         auto pos = (query.total_message_count - query.awaited_message_count + 1);