Steps to reproduce:

Create dashboard, add widget "Problems by severity".

Result:

• Undefined offset: 7906406 [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() in include/actions.inc.php:1737]
• Argument 1 passed to makeEventMessagesIcon() must be of the type array, null given, called in /var/www/frontends/php/include/actions.inc.php on line 1737 and defined [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() → makeEventMessagesIcon() in include/actions.inc.php:1766]
• Undefined offset: 7906406 [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() in include/actions.inc.php:1738]
• Argument 1 passed to makeEventSeverityChangesIcon() must be of the type array, null given, called in /var/www/frontends/php/include/actions.inc.php on line 1738 and defined [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() → makeEventSeverityChangesIcon() in include/actions.inc.php:1820]
• Undefined offset: 7906406 [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() in include/actions.inc.php:1739]
• Argument 1 passed to makeEventActionsIcon() must be of the type array, null given, called in /var/www/frontends/php/include/actions.inc.php on line 1739 and defined [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CView->getOutput() → include() → makeSystemStatus() → makeProblemsPopup() → makeEventActionsIcons() → makeEventActionsIcon() in include/actions.inc.php:1897]