message: Only process change if in the stack
diff: @@ -42,7 +42,7 @@ class Scene extends React.Component<SceneProps, SceneState> {
  onWillAppear() {
  var {crumb, navigationEvent} = this.props;
  var {crumbs, nextCrumb} = navigationEvent.stateNavigator.stateContext;
  - var changed = !this.state.navigationEvent;
  + var changed = !this.state.navigationEvent && crumb < crumbs.length;
  if (!changed && crumb < crumbs.length) {
  var {state: latestState, data: latestData} = crumbs[crumb];
  var {state, data} = this.state.navigationEvent.stateNavigator.stateContext;
  