Steps to reproduce:

1. Create "Host A"
2. Add two items to host item1 and item2
3. Create classic graph widget
4. Select "Simple graph" and add item1
5. Check "Dynamic item" and save widget and dashboard
6. Set the refresh interval for widget "10 seconds"
7. In another browser tab go to items and delete item1
8. Go back to tab with Dashboard and wait until red unstyled error message appears in widget "No permissions to referred object or it does not exist!"
9. Select "Host A" in dashboard controls

Result: other item "item2" appears in the widget and an error

Undefined offset: 0 [zabbix.php:22 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerWidgetGraphView->doAction() → CConfigFile->{closure}() in conf/zabbix.conf.php:86]
Trying to access array offset on value of type null [zabbix.php:22 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerWidgetGraphView->doAction() → CConfigFile->{closure}() in conf/zabbix.conf.php:86]

Expected: stylized gray error "No permissions to referred object or it does not exist!" in widget (the same as after page refresh)