Fix IntersectionObserver error for server

src/app/app.component.ts

@@ -162,7 +162,7 @@ export class AppComponent {
     this.subscriptions.forEach(value => {
       if (value instanceof Subscriber) {
         value.unsubscribe();
-      } else if (value instanceof IntersectionObserver) {
+      } else if (typeof IntersectionObserver !== "undefined" && value instanceof IntersectionObserver) {
         value.disconnect();
       }
     });