null cannot be cast to non-null type android.view.ViewGroup

[hedongfu]

com.afollestad.aesthetic.utils.ActivityExtKt.getRootView (ActivityExtKt.java)
com.afollestad.aesthetic.internal.AestheticExtKt.addBackgroundSubscriber (AestheticExtKt.java)
com.afollestad.aesthetic.Aesthetic$Companion$$special$$inlined$subscribeTo$3.accept (Aesthetic.java)
io.reactivex.internal.observers.LambdaObserver.isDisposed (LambdaObserver.java)
io.reactivex.internal.operators.observable.ObservableDistinctUntilChanged$DistinctUntilChangedObserver.onNext (ObservableDistinctUntilChanged.java)
io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.drainNormal (ObservableObserveOn.java)
io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.run (ObservableObserveOn.java)
io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run (HandlerScheduler.java)

Guidelines

1. You must run the spotlessApply task before commiting, either through Android Studio or with ./gradlew spotlessApply.
2. A PR should be focused and contained. If you are changing multiple unrelated things, they should be in separate PRs.
3. A PR should fix a bug or solve a problem - something that only you would use is not necessarily something that should be published.
4. Give your PR a detailed title and description - look over your code one last time before actually creating the PR. Give it a self-review.

If you do not follow the guidelines, your PR will be rejected.