title: what is the question mark in an angular template?
body: <p>I'm checking out angular firebase documentation and I see this:</p>
  
  <pre><code>@Component({
    selector: 'app-root',
    template: `
    &lt;h1&gt;{{ (item | async)?.name }}&lt;/h1&gt;
    `,
  })
  export class AppComponent {
    item: FirebaseObjectObservable&lt;any&gt;;
    constructor(db: AngularFireDatabase) {
      this.item = db.object('/item');
    }
  }
  </code></pre>
  
  <p>what does the <code>?</code> sign after <code>(item | async)</code> do?</p>
  
  <p>Isn't it ok anyway to do <code>undefined.someProperty</code> in the template?</p>