[node-notifier] Enable strictNullChecks (#43642)
[node-notifier] Enable strictNullChecks (#43642)


georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,mcliment/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,markogresak/DefinitelyTyped,dsebastien/DefinitelyTyped