message: Stored tab bar item in reactSubviews
  Didn't think reactSubviews was still around in new arch but it is
diff: @@ -111,7 +111,7 @@ using namespace facebook::react;
  -(void) selectTab
  {
  _nativeEventCount++;
  - NVTabBarItemComponentView *tabBarItem = (NVTabBarItemComponentView *)self.subviews[_selectedTab];
  + NVTabBarItemComponentView *tabBarItem = (NVTabBarItemComponentView *)self.reactSubviews[_selectedTab];
  /*self.onTabSelected(@{
  @"tab": @(_selectedTab),
  @"eventCount": @(_nativeEventCount),
  @@ -125,6 +125,7 @@ using namespace facebook::react;
  - (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index
  {
  + [super insertReactSubview:childComponentView atIndex:index];
  NSMutableArray *controllers = [NSMutableArray arrayWithArray:[_tabBarController viewControllers]];
  [controllers insertObject:[(NVTabBarItemComponentView *) childComponentView navigationController] atIndex:index];
  [_tabBarController setViewControllers:controllers];
  @@ -132,6 +133,7 @@ using namespace facebook::react;
  - (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index
  {
  + [self.reactSubviews indexOfObject:childComponentView];
  NSMutableArray *controllers = [NSMutableArray arrayWithArray:[_tabBarController viewControllers]];
  [controllers removeObjectAtIndex:index];
  [_tabBarController setViewControllers:controllers];
  