i'm using https://www.koolreport.com/examples/reports/drilldown/drilldown/index.php Setup with 2 fields as for the example, but i have this error:
Fatal error: Uncaught Error: Call to a member function format() on boolean in /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/processes/DateTimeFormat.php:71 Stack trace: #0
/var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/core/Node.php(92): koolreport\processes\DateTimeFormat->onInput(Array) #1 /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/core/Node.php(68): koolreport\core\Node->input(Array, Object(koolreport\processes\CopyColumn)) #2 /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/processes/CopyColumn.php(41): koolreport\core\Node->next(Array) #3 /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/core/Node.php(92): koolreport\processes\CopyColumn->onInput(Array) #4 /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/core/Node.php(68): koolreport\core\Node->input(Array, Object(koolreport\da in /var/www/vhosts/xxxxxxxxx/vendor/koolphp/koolreport/koolreport/processes/DateTimeFormat.php on line 71