Jestliže chceme, aby prošly i položky s nevyplněným polem "konec", upravíme soubor
views_between_dates_filter\includes\views_between_dates_filter_handler.inc

ř. 72-74:

if ($this->operator == '=') {
  $this->query->add_where_expression($group, "$start_field <= $placeholder AND ($end_field >= $placeholder OR $end_field IS NULL)", array($placeholder => $value));
      }