1. Go to services and select existing service or create a new one.
2. For trigger field, press "Select" button.
3. Observe the hidden error in output file:

• 4.0: Undefined index: [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->{closure}() in app\views\popup.generic.php:279]
• 4.2 (trunk) Undefined index: [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->{closure}() in app\views\popup.generic.php:280]

Two lines of errors generated for each trigger in popup.