message: If exit animation not found use default
  If use 0 then the crumb scene disappears immediately. To be consistent with activiities want a not found to keep the crumb unmoved
diff: @@ -31,6 +31,8 @@ class FragmentNavigator extends SceneNavigator {
  final FragmentManager fragmentManager = ((FragmentActivity) activity).getSupportFragmentManager();
  int enter = getAnimationResourceId(activity, stack.enterAnim, android.R.attr.activityOpenEnterAnimation);
  int exit = getAnimationResourceId(activity, stack.exitAnim, android.R.attr.activityOpenExitAnimation);
  + if (exit == 0 && stack.exitAnim != null)
  + exit = getAnimationResourceId(activity, null, android.R.attr.activityOpenExitAnimation);
  for(int i = 0; i < crumb - currentCrumb; i++) {
  int nextCrumb = currentCrumb + i + 1;
  String key = stack.keys.getString(nextCrumb);
  