Don't check external messages if out of sync

Author: SpyCheese

validator/manager.cpp

@@ -430,6 +430,10 @@ void ValidatorManagerImpl::add_external_message(td::Ref<ExtMessage> msg, int pri
   ext_messages_hashes_[id.hash] = {priority, id};
 }
 void ValidatorManagerImpl::check_external_message(td::BufferSlice data, td::Promise<td::Ref<ExtMessage>> promise) {
+  if (!started_) {
+    promise.set_error(td::Status::Error(ErrorCode::notready, "node not synced"));
+    return;
+  }
   auto state = do_get_last_liteserver_state();
   if (state.is_null()) {
     promise.set_error(td::Status::Error(ErrorCode::notready, "not ready"));