Handle events overview when event definition is missing (6.3)#25736

ryan-carroll-graylog merged 1 commit into6.3Graylog2/graylog2-server:6.3from

backport-6.3/13756-when-an-event-definition-has-been-removed-the-events-overview-widget-will-error-when-trying-to-reference-itGraylog2/graylog2-server:backport-6.3/13756-when-an-event-definition-has-been-removed-the-events-overview-widget-will-error-when-trying-to-reference-itCopy head branch name to clipboard