title: Ionic2 Deep linking segment optional params
body: <p>I cannot find a single document that explains how to use optional params in segments.</p>
  
  <p>In my app.module.ts I have this deepLinkConfig : </p>
  
  <pre><code>let deepLinkConfig = {
    links: [{
      component: HomePage, name: 'Home', segment: 'home'
    }, {
      component: ConnexionPage, name: 'Connexion', segment: 'connexion'
    }, {
      component: InscriptionPage, name: 'Inscription', segment: 'inscription'
    }, {
      component: ProfilePage, name: 'Profile', segment: 'profile/:userId'
    }, {
      component: ExplorePage, name: 'Explore', segment: 'explore'
    }, {
      component: FAQPage, name: 'FAQ', segment: 'faq'
    }]
  };
  
  ...
  imports: [
      ...
      IonicModule.forRoot(MyApp, {}, deepLinkConfig);
  ],
  </code></pre>
  
  <p>The user should be able to access his profile via <code>/profile</code>, but also consult another user's profile with <code>/profile/:userId</code>. But when I try to access /profile, I get an error :</p>
  
  <blockquote>
    <p>Uncaught (in promise): invalid views to insert</p>
  </blockquote>
  
  <p>Via navCtrl, it's possible to go to 'profile' with an empty string as the userId, but once you actualize the page, it goes blank.</p>
  
  <p>Is there a way to make the params optional in deeplinking ?</p>