Observables (angular 2) doesn't return empty data
<p>I'm trying this tutorial <a href="http://plnkr.co/edit/?p=preview" rel="nofollow noreferrer">http://plnkr.co/edit/?p=preview</a>
And I want to execute wiki smart component if user input more then 3 chars.
I did this changes</p>

<pre><code>  items:Observable&lt;string[]&gt; = this._searchTermStream
    .debounceTime(300)
    .distinctUntilChanged()
    .switchMap((term:string) =&gt; {
        if (term.length &gt; 3) {
          return this._wikipediaService.search(term);
        } else {
          return Observable.empty();
        }
    }
</code></pre>

<p>but it doesn't work. Still shows old founded data. But I want to show nothing.</p>