fix(docs-infra): initialize events arrays in EventsComponent (#47458)

initialize the events fields of the EventsComponent so that
they are always defined

PR Close #47458

aio/src/app/custom-elements/events/events.component.html

@@ -1,5 +1,5 @@
 <h2>Where we'll be presenting:</h2>
-<ng-container [ngSwitch]="!!upcomingEvents?.length">
+<ng-container [ngSwitch]="!!upcomingEvents.length">
   <div *ngSwitchCase="false">
     <p>We don't have any upcoming speaking engagements at the moment.</p>
     <p>

aio/src/app/custom-elements/events/events.component.spec.ts

@@ -20,11 +20,11 @@ describe('EventsComponent', () => {
   });
 
   it('should have no pastEvents when first created', () => {
-    expect(component.pastEvents).toBeUndefined();
+    expect(component.pastEvents.length).toEqual(0);
   });
 
   it('should have no upcoming when first created', () => {
-    expect(component.upcomingEvents).toBeUndefined();
+    expect(component.upcomingEvents.length).toEqual(0);
   });
 
   describe('ngOnInit()', () => {

aio/src/app/custom-elements/events/events.component.ts

@@ -18,8 +18,8 @@ export interface AngularEvent {
 })
 export class EventsComponent implements OnInit {
 
-  pastEvents: AngularEvent[];
-  upcomingEvents: AngularEvent[];
+  pastEvents: AngularEvent[] = [];
+  upcomingEvents: AngularEvent[] = [];
 
   constructor(private eventsService: EventsService) { }