title: InvalidPipeArgument: '' for pipe 'AsyncPipe'
body: <pre><code>  timers: Observable&lt;ITimer&gt;[]=[];
  </code></pre>
  
  <p>Template is:</p>
  
  <pre><code>&lt;div *ngFor="let item of timers | async"&gt;
    {{ item.time }}
    &lt;div (click)="remove(item.index)"&gt;Remove&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Why I get this error?</p>
  
  <p>If not initialize <code>this.timers</code> then async works. Elsewise I can not get lenght in this  method:</p>
  
  <pre><code> add() {
      let options = {
        finishDate: null,
        time: null,
        index: this.timers.length
      };
  
      this.timers.push(this.create(options));
  
    }
  </code></pre>
  
  <p>In line: <code>index: this.timers.length</code></p>