title: Forkjoin with empty (or not) array of observables
body: <p>I'm trying to detect when all my observables have completed. I have the following Observables:</p>
  
  <pre class="lang-js prettyprint-override"><code>let observables:any[] = [];
  if(valid){
      observables.push(new Observable((observer:any) =&gt; {
          async(()=&gt;{
              observer.next();
              observer.complete();
          })
      }))
  }
  if(confirmed){
      observables.push(new Observable((observer:any) =&gt; {
          async(()=&gt;{
              observer.next();
              observer.complete();
          })
      }))
  }
  
  Observable.forkJoin(observables).subscribe(
      data =&gt; {
          console.log('all completed');
      },
      error =&gt; {
          console.log(error);
      }
  );
  </code></pre>
  
  <p>I need to do something whenever all my functions are completed. Forkjoin seems to work when the <code>observables</code> array is not empty. But when the array is empty, it never gets called. How can I solve this?</p>