message: Fix query result
diff: @@ -135,7 +135,7 @@ private:
  base_row += chunk->size();
  chunk = result->Fetch();
  current_row.row = 0;
  - if (chunk->size() == 0) {
  + if (!chunk || chunk->size() == 0) {
  // exhausted all rows
  base_row = 0;
  result = nullptr;
  