public function getValues()
    {
        // When there's no data and the filter itself is not required,
        // we don't return values
        if (!$this->data && !$this->isRequired()) {
            return null;
        }

        // Don't return any values when "inputsToFilter" is set to empty array
        if (!$this->needsFiltering()) {
            return array();
        }

        return parent::getValues();
    }