title: Return an empty Observable
body: <p>The function <code>more()</code> is supposed to return an <code>Observable</code> from a get request</p>
  <pre class="lang-ts prettyprint-override"><code>export class Collection {
    public more = (): Observable&lt;Response&gt; =&gt; {
      if (this.hasMore()) {
        return this.fetch();
      } else {
        // return empty observable
      }
    };
  
    private fetch = (): Observable&lt;Response&gt; =&gt; {
      return this.http.get(&quot;some-url&quot;).map((res) =&gt; {
        return res.json();
      });
    };
  }
  </code></pre>
  <p>In this case I can only do a request if <code>hasMore()</code> is true, else I get an error on <code>subscribe()</code> function <code>subscribe is not defined</code>, how can I return an empty Observable?</p>
  <pre class="lang-ts prettyprint-override"><code>this.collection.more().subscribe(
    (res) =&gt; {
      console.log(res);
    }, (err) =&gt; {
      console.log(err);
    }
  );
  </code></pre>