title: undefined is not an object (evaluating '_reactNative.BackHandler.addEventListener')
body: <p>I am using <strong>react-native: 0.40 with react: 15.4.2 and react-native-router-flux: 3.37.0</strong> and I've been getting this error. Although everything I get this error on iOS, the app runs with no issue. But on Android, whenever I press the back button, the app crashes.</p>
  
  <p>My assumption is that react native back button is conflicting with react-native-router-flux package.</p>
  
  <p>Any help would be appreciated.</p>
  
  <p><a href="https://i.stack.imgur.com/JeyYZ.png" rel="nofollow noreferrer">evaluating '_reactNative.BackHandler.addEventListener'</a></p>