message: Hid the titlebar children on ios if navigation bar hidden
  In the zoom example, the title bar appeared briefly when the navigation bar was hidden on the details scene
diff: @@ -23,7 +23,7 @@ class NavigationBar extends React.Component<any, any> {
  hidden={hidden}
  style={{height: Platform.OS === 'android' && collapsingBar ? style.height : null}}
  {...otherProps}>
  - {Platform.OS === 'ios' ? children :
  + {Platform.OS === 'ios' ? !hidden && children :
  <Container
  collapse={!!collapsingBar}
  {...otherProps}
  