docs: protected void checkResultSet(int column) throws SQLException {
      checkClosed();
      if (thisRow == null) {
        throw new PSQLException(
            GT.tr("ResultSet not positioned properly, perhaps you need to call next."),
            PSQLState.INVALID_CURSOR_STATE);
      }
      checkColumnIndex(column);
      wasNullFlag = (thisRow[column - 1] == null);
    }