title: setOnNavigatorEvent callback not fired when switching tabs
body: <p>I am working on an app powered by <code>react-native@0.55.4</code> and <code>react-native-navigation@1.1.474</code>.</p>
  
  <p>Initially, there is only a login screen (using <code>Navigation.startSingleScreenApp</code>). When the user logs in I call <code>Navigation.startTabBasedApp</code> (one of the tab components is my <code>NavScreen</code>). Whenever the user changes to another tab the root of the tab's stack is supposed to be displayed so I tried something like this:</p>
  
  <pre><code>class NavScreen extends React.PureComponent {
      constructor(props) {
          super(props)
          this.props.navigator.setOnNavigatorEvent(this.toRootOnTabSelect.bind(this))
      }
  
      toRootOnTabSelect(event) {
          const {id} = event
          if (["bottomTabSelected", "bottomTabReselected"].includes(id)) {
              this.props.navigator.popToRoot({
                  animated: true,
                  animationType: "fade",
              })
          }
      }
  
      render() {
          return &lt;Text&gt;Whatever...&lt;/Text&gt;
      }
  }
  </code></pre>
  
  <p>But for some reason my <code>toRootOnTabSelect</code> event handler method is not being called when I change tabs (by clicking on them - not by calling the <code>switchToTab</code> API method).</p>
  
  <p>There are multiple posts I found online (i.e. <a href="https://stackoverflow.com/a/51159091/6928824">https://stackoverflow.com/a/51159091/6928824</a>, <a href="https://github.com/wix/react-native-navigation/issues/648" rel="nofollow noreferrer">https://github.com/wix/react-native-navigation/issues/648</a>) that indicate that it should work so I don't know what I'm missing. :/</p>
  
  <p>Any help is greatly appreciated! :)</p>