title: React Navigation headerBackImage not working
body: <p>I'm using React Navigation 3.11 in my React Native app and I want to customize the back button in stack navigation. In the <a href="https://reactnavigation.org/docs/en/stack-navigator.html#headerbackimage" rel="noreferrer">docs</a> it says:</p>
  
  <blockquote>
    <p><strong>headerBackImage</strong></p>
    
    <p>React Element or Component to display custom image in header's back
    button. When a component is used, it receives a number of props when
    rendered (tintColor, title). Defaults to Image component with
    react-navigation/views/assets/back-icon.png back image source, which
    is the default back icon image for the platform (a chevron on iOS and
    an arrow on Android).</p>
  </blockquote>
  
  <p>Here is my configuration:</p>
  
  <pre><code>let navigationRouteConfigMap : NavigationRouteConfigMap = {
        _main:
        {screen: page, navigationOptions: 
          { 
            [...]
            headerBackTitle: '',
            headerTruncatedBackTitle: '',
            headerBackImage: Images.backArrow,
          }
        }
  
      }
      let stackNavigatorConfig:StackNavigatorConfig = {
        headerBackTitleVisible: false
      }
  
      return createStackNavigator(navigationRouteConfigMap, stackNavigatorConfig)
  </code></pre>
  
  <p>I've got other pages as well in my config, <em>all</em> having the same shared navigation options with custom header back image. However, in my app it renders the default back arrow. (<code>headerBackTitleVisible: false</code> does work though)</p>
  
  <p>What am I doing wrong?</p>