message: Skipped shared elements if fluently navigated
  Fluently navigate from A --> B --> C and navigate back one to B. If sharedElements return non-empty array then it went down the finishAfterTransition path. But postponeEnterTransition hadn't been called on B, because B was fluently navigated over, so it threw and error.
diff: @@ -94,7 +94,8 @@ public class NavigationStackView extends ViewGroup {
  int enter = this.getAnimationResourceId(enterAnim, this.activityCloseEnterAnimationId);
  int exit = this.getAnimationResourceId(exitAnim, this.activityCloseExitAnimationId);
  final HashMap<String, View> oldSharedElementsMap = getSharedElementMap();
  - Pair[] oldSharedElements = currentCrumb - crumb == 1 ? getSharedElements(oldSharedElementsMap, oldSharedElementNames) : null;
  + Boolean shared = currentActivity.getIntent().getSerializableExtra(SceneActivity.SHARED_ELEMENTS) != null;
  + Pair[] oldSharedElements = (shared && currentCrumb - crumb == 1) ? getSharedElements(oldSharedElementsMap, oldSharedElementNames) : null;
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && oldSharedElements != null && oldSharedElements.length != 0) {
  final SharedElementTransitioner transitioner = new SharedElementTransitioner(currentActivity, getSharedElementSet(oldSharedElementNames));
  currentActivity.setEnterSharedElementCallback(new SharedElementCallback() {
  