title: React-native-navigation not returning from inside a component
body: <p>I am using react native navigation by wix for my application.</p>
  
  <p>It is working fine if I just have the <code>Navigation.startTabBasedApp</code> in my application like this: </p>
  
  <pre><code>import React, { Component } from 'react';
  import Amplify from 'aws-amplify-react-native';
  import { Navigation } from 'react-native-navigation';
  import { registerScreens } from './screens';
  import aws_exports from './aws-exports';
  
  Amplify.configure(aws_exports);
  
  registerScreens();
  
  return Navigation.startTabBasedApp({
    tabs: [
      {
        label: 'Home',
        screen: 'pumped.HomeScreen',
        title: 'Pumped',
      },
      {
        label: 'Sell',
        screen: 'pumped.ListScreen',
        title: 'Sell an item',
      },
      {
        label: 'Profile',
        screen: 'pumped.ProfileScreen',
        title: 'Profile',
      },
    ],
  });
  </code></pre>
  
  <p>However I want to render either a single screen or this tab based app conditionally based on wether the user is signed in or not. But when i add the two inside a app component and return either one based on a condition (true in my code just for testing) it doesn't return anything?</p>
  
  <p>Here is my code:</p>
  
  <pre><code>import React, { Component } from 'react';
  import Amplify from 'aws-amplify-react-native';
  import { Navigation } from 'react-native-navigation';
  import { registerScreens } from './screens';
  import aws_exports from './aws-exports';
  
  Amplify.configure(aws_exports);
  
  registerScreens();
  
  class App extends Component {
    render() {
      if (true) {
        return Navigation.startSingleScreenApp({
          screen: {
            screen: 'pumped.RegisterScreen',
            navigatorStyle: {},
            navigatorButtons: {},
            title: 'Register',
          },
        });
      }
      return Navigation.startTabBasedApp({
        tabs: [
          {
            label: 'Home',
            screen: 'pumped.HomeScreen',
            title: 'Pumped',
          },
          {
            label: 'Sell',
            screen: 'pumped.ListScreen',
            title: 'Sell an item',
          },
          {
            label: 'Profile',
            screen: 'pumped.ProfileScreen',
            title: 'Profile',
          },
        ],
      });
    }
  }
  
  export default App;
  </code></pre>
  
  <p>Thanks.</p>