message: Fixed a groupby glitch
diff: @@ -1099,12 +1099,8 @@ groupby (F &&func, const char *gb_col_name, sort_state already_sorted) const {
  DataFrame tmp_df = *this;
  - if (already_sorted == sort_state::not_sorted) {
  - if (gb_col_name == nullptr) {
  - tmp_df.sort<T, Ts ...>(DF_INDEX_COL_NAME, sort_spec::ascen);
  - }
  - else { tmp_df.sort<T, Ts ...>(gb_col_name, sort_spec::ascen); }
  - }
  + if (already_sorted == sort_state::not_sorted)
  + tmp_df.sort<T, Ts ...>(gb_col_name, sort_spec::ascen);
  DataFrame result;
  