title: How to go back when a Stack Navigator is nested within another Stack Navigator? Without two headers appearing?
body: <p>Pretty much the same problem everyone else has seemed to have but I have not come up with a solution.  When I nest a stack navigator there is two headers.  I can remove the nested header using { header: null } or even that header mode option.  Well the problem is,(which has been pointed out here numerous times <a href="https://github.com/react-navigation/react-navigation/issues/88" rel="nofollow noreferrer">https://github.com/react-navigation/react-navigation/issues/88</a>), that this is the root header.  So there is no back button available.  How can I remove the root header and keep the nested header?  I'm able to pull something similar with a tab bar.  I do:</p>
  
  <pre><code>navigatorName.navigationOptions = ({navigation}) =&gt; {
  let tabBarVisible = true;
  if (navigation.state.index &gt; 0) {
      tabBarVisible = false;
  }
  return { tabBarVisible }};
  </code></pre>
  
  <p>I tried doing this by setting header to null but it didn't seem to work?  Any suggestions?</p>
  
  <p>EDIT: Here is my code</p>
  
  <pre><code>const BatteryListStackNavigator = createStackNavigator({
  BatteryList: BatteryList,
  BatteryDetails: BatteryDetailsBottomTabNavigator,
  });
  
  const RouteListStackNavigator = createStackNavigator({
  RouteList: RouteList,
  BatteryList: BatteryListStackNavigator,
  });
  
  RouteListStackNavigator.navigationOptions = ({ navigation }) =&gt; {
  let tabBarVisible = true;
  if (navigation.state.index &gt; 0) {
      tabBarVisible = false;
  }
  
  return {
      tabBarVisible,
  };
  };
  
  const IndexBottomTabNavigator = createBottomTabNavigator(
  {
      Home: Home,
      RouteList: RouteListStackNavigator,
      Alerts: Alerts,
  }
  );
  
  const AppSwitchNavigator = createSwitchNavigator(
  {
      Login: Login,
      Application: IndexBottomTabNavigator,
  },
  {
      initialRouteName: 'Login',
  },
  );
  </code></pre>
  
  <p>If I set it like this:</p>
  
  <pre><code>const BatteryListStackNavigator = createStackNavigator(
  {
      BatteryList: BatteryList,
      BatteryDetails: BatteryDetailsBottomTabNavigator,
  },
  {
      headerMode: 'none',
  },
  );
  </code></pre>
  
  <p>It works on the way through but when I get back it disappears? Which I'm guessing is because its still the root one so on the third, the back button takes you all the way to the first...</p>
  
  <p>I'm trying to set it in the sameplace I have the tabBarVisible.. I've tried header: null, headerMode: 'none'.  None of them seem to be working in that navigationsOptions function I am doing.</p>
  
  <p>Edit: should I just set all subsequent headers after the first stack navigation to none and then just programatically set my back buttons based on everything?  I think this is what i'm going to do. </p>