Make trigger action which results in Script execution if Trigger is fired.
Immediately open Reports->Action log to see In progress status for this action.

No matter if Script is executed successfully or failed, while Status column is In progress there is runtime error written in apache2 log:

Trying to access array offset on value of type null [zabbix.php:17 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> ZBase->processResponseFinal() -> CView->getOutput() -> include() -> CConfigFile->{closure}() in app/views/reports.actionlog.list.php:150]

The exact 100% reproducible case here: ZBX-24800 (1).