Hide the button toolbar when setting navigationButtonsHidden to YES

The comments of "navigationButtonsHidden" says "on iPhone, hides the bottom toolbar".

However, when I set navigationButtonsHidden to YES after creating an TOWebViewController, the buttons are hidden, but the bottom toolbar itself remains.

I changed the code based on my understanding, because I think "navigationButtonsHidden" is used to hide the entire bottom toolbar.

Please check it, thank you!