title: Back Button not showing with Stack.Navigator
body: <p>I'm trying to implement a simple navigation but for some reason back button it's not showing up.</p>
  <p>My Main Component</p>
  <pre class="lang-js prettyprint-override"><code>    &lt;NavigationContainer&gt;
        &lt;Stack.Navigator&gt;
          {userToken ? (
            &lt;Stack.Screen name={routesName.App} component={TabNavigator} /&gt;
          ) : (
            &lt;Stack.Screen name={routesName.Auth} component={AuthStack} /&gt;
          )}
        &lt;/Stack.Navigator&gt;
      &lt;/NavigationContainer&gt;
  </code></pre>
  <p>Tab Navigation</p>
  <pre class="lang-js prettyprint-override"><code>const TabNavigator = () =&gt; {
    return (
      &lt;Tab.Navigator&gt;
        &lt;Tab.Screen name={routesName.Home} component={HomeStack} /&gt;
        &lt;Tab.Screen name={routesName.Settings} component={SettingsStack} /&gt;
      &lt;/Tab.Navigator&gt;
    );
  };
  </code></pre>
  <pre class="lang-js prettyprint-override"><code>const HomeStack = () =&gt; {
    return (
      &lt;Stack.Navigator initialRouteName={routesName.Home}&gt;
        &lt;Stack.Screen name={routesName.Home} component={HomeScreen} /&gt;
        &lt;Stack.Screen name={routesName.Details} component={DetailsScreen} /&gt;
      &lt;/Stack.Navigator&gt;
    );
  };
  </code></pre>
  <pre class="lang-js prettyprint-override"><code>const SettingsStack = () =&gt; {
    return (
      &lt;Stack.Navigator&gt;
        &lt;Stack.Screen name={routesName.Settings} component={SettingsScreen} /&gt;
        &lt;Stack.Screen name={routesName.Profile} component={ProfileScreen} /&gt;
      &lt;/Stack.Navigator&gt;
    );
  };
  </code></pre>
  <p>No matter what screen i go, app headers always shows &quot;App&quot; as title.</p>
  <img src="https://i.stack.imgur.com/TbcG2.jpg" width="200">
  <img src="https://i.stack.imgur.com/Z2srL.png[![enter%20image%20description%20here][1]][1]" width="200">
  <img src="https://i.stack.imgur.com/xg2Rl.png[![enter%20image%20description%20here][1]][1]" width="200">
  <img src="https://i.stack.imgur.com/8ocFP.png" width="200">