title: Stuck in endless loop when not dispatching an action in ngrx/effects
body: <p>I'm using Angular2 and ngrx/store and ngrx/effects for state management. </p>
  
  <p>When a certain action fails I want to show an error message but it seems that I can't perform this task in an <code>@Effects()</code> block. See the following: </p>
  
  <pre><code>  @Effect() selectOfficeFail$ = this.actions$
     .ofType(SelectOfficeActions.LOAD_FAIL)
     .do(() =&gt; {
       alert('Error! No offices found!'); // I keep entering here
    });
  </code></pre>
  
  <p>When the code above runs the alert is run endless number of times until the browser crashes. It seems an <code>@Effect()</code> <strong>has to</strong> return a new <code>dispatch()</code> but I don't understand why. And why does the alert() above run endless number of times?</p>
  
  <p><strong>Edit:</strong> I am <strong>not</strong> dispatching <code>SelectOfficeActions.LOAD_FAIL</code> multiple times. Only once</p>