Handle events overview when event definition is missing (6.2)#25737

ryan-carroll-graylog wants to merge 1 commit into6.2Graylog2/graylog2-server:6.2from

backport-6.2/13756-when-an-event-definition-has-been-removed-the-events-overview-widget-will-error-when-trying-to-reference-itGraylog2/graylog2-server:backport-6.2/13756-when-an-event-definition-has-been-removed-the-events-overview-widget-will-error-when-trying-to-reference-itCopy head branch name to clipboard