Undefined indexes in maintenance popup

Undefined index: timeperiodid [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:31]
Undefined index: hour [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CController->run() -> CControllerPopupMaintenancePeriod->doAction() -> CConfigFile->\{closure}() in app\controllers\CControllerPopupMaintenancePeriod.php:192]
Undefined index: minute [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CController->run() -> CControllerPopupMaintenancePeriod->doAction() -> CConfigFile->\{closure}() in app\controllers\CControllerPopupMaintenancePeriod.php:192]
Undefined index: timeperiodid [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:31]
Undefined index: month_date_type [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:99]
Undefined index: month_date_type [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:123]
Undefined index: hour [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:137]
Undefined index: minute [zabbix.php:21 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> CView->getOutput() -> include() -> CConfigFile->\{closure}() in app\views\popup.maintenance.period.php:139]

1. Open Configuration > Maintenance.
2. Press Create.
3. Go to Periods tab.
4. Click "Add" (already 1 undefined index)
5. Enter value and press "Add" in popup.
6. Observe undefined indexes.