DualNavigationMapActivity NullPointerException when adding route

[danesfeder]

Found 🐛 in DualNavigationMapActivity during CI:

FATAL EXCEPTION: main
Process: com.mapbox.services.android.navigation.testapp, PID: 11145
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.mapbox.services.android.navigation.ui.v5.route.NavigationMapRoute.addRoutes(java.util.List)' on a null object reference
	at com.mapbox.services.android.navigation.testapp.activity.navigationui.DualNavigationMapActivity.onResponse(DualNavigationMapActivity.java:121)
	at com.mapbox.api.directions.v5.MapboxDirections$1.onResponse(MapboxDirections.java:169)
	at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:70)
	at android.os.Handler.handleCallback(Handler.java:739)
	at android.os.Handler.dispatchMessage(Handler.java:95)
	at android.os.Looper.loop(Looper.java:135)
	at android.app.ActivityThread.main(ActivityThread.java:5254)
	at java.lang.reflect.Method.invoke(Native Method)
	at java.lang.reflect.Method.invoke(Method.java:372)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

It looks like the route response is being returned before the map is ready and we are trying to add the routes via NavigationRoute#addRoutes.