MapboxNavigation#getCameraEngine NullPointerException

[Guardiola31337]

Found 🐛 in DualNavigationMapActivity during CI:

FATAL EXCEPTION: ControllerMessenger
Process: com.mapbox.services.android.navigation.testapp, PID: 25332
java.lang.RuntimeException: Unable to destroy activity {com.mapbox.services.android.navigation.testapp/com.mapbox.services.android.navigation.testapp.activity.navigationui.EndNavigationActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.mapbox.services.android.navigation.v5.navigation.camera.Camera com.mapbox.services.android.navigation.v5.navigation.MapboxNavigation.getCameraEngine()' on a null object reference
	at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3706)
	at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3724)
	at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3924)
	at android.app.ActivityThread.access$900(ActivityThread.java:151)
	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1309)
	at android.os.Handler.dispatchMessage(Handler.java:102)
	at androidx.test.espresso.base.Interrogator.a(Interrogator.java:19)
	at androidx.test.espresso.base.UiControllerImpl.a(UiControllerImpl.java:142)
	at androidx.test.espresso.base.UiControllerImpl.a(UiControllerImpl.java:134)
	at androidx.test.espresso.base.UiControllerImpl.a(UiControllerImpl.java:34)
	at androidx.test.espresso.action.MotionEvents.a(MotionEvents.java:74)
	at androidx.test.espresso.action.MotionEvents.a(MotionEvents.java:52)
	at androidx.test.espresso.action.Tap.c(Tap.java:9)
	at androidx.test.espresso.action.Tap.a(Tap.java:19)
	at androidx.test.espresso.action.Tap$1.b(Tap.java:2)
	at androidx.test.espresso.action.GeneralClickAction.perform(GeneralClickAction.java:22)
	at androidx.test.espresso.ViewInteraction$SingleExecutionViewAction.perform(ViewInteraction.java:9)
	at androidx.test.espresso.ViewInteraction.a(ViewInteraction.java:78)
	at androidx.test.espresso.ViewInteraction.a(ViewInteraction.java:94)
	at androidx.test.espresso.ViewInteraction$1.call(ViewInteraction.java:3)
	at java.util.concurrent.FutureTask.run(FutureTask.java:237)
	at android.os.Handler.handleCallback(Handler.java:739)
	at android.os.Handler.dispatchMessage(Handler.java:95)
	at android.os.Looper.loop(Looper.java:135)
	at android.app.ActivityThread.main(ActivityThread.java:5254)
	at java.lang.reflect.Method.invoke(Native Method)
	at java.lang.reflect.Method.invoke(Method.java:372)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.mapbox.services.android.navigation.v5.navigation.camera.Camera com.mapbox.services.android.navigation.v5.navigation.MapboxNavigation.getCameraEngine()' on a null object reference
	at com.mapbox.services.android.navigation.ui.v5.NavigationViewModel.onDestroy(NavigationViewModel.java:102)
	at com.mapbox.services.android.navigation.ui.v5.NavigationView.shutdown(NavigationView.java:571)
	at com.mapbox.services.android.navigation.ui.v5.NavigationView.onDestroy(NavigationView.java:165)
	at com.mapbox.services.android.navigation.testapp.activity.navigationui.EndNavigationActivity.onDestroy(EndNavigationActivity.java:250)
	at android.app.Activity.performDestroy(Activity.java:6169)
	at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1141)
	at androidx.test.runner.MonitoringInstrumentation.callActivityOnDestroy(MonitoringInstrumentation.java:208)
	at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3693)
	... 28 more

Pretty easy to reproduce opening and closing DualNavigationMapActivity from the test app.

I think a regression from #1167