Navigation bar's buttons tint color sometimes not set
<p>Refer to the following, short video: <a href="http://screencast.com/t/cmnsqVTh" rel="nofollow">http://screencast.com/t/cmnsqVTh</a></p>

<p>The problem is with the color of a navigation bar's back button.</p>

<p>The first time I load the app, the navigation bar + its buttons have the default color. I then push a view controller on the stack, and when the new view loads (in the viewDidLoad method), it sets the navigation bar's tint color to pink. The nav bar's buttons are also pink as expected. 
I then press the back button, and the view is popped from the stack. On the root view controller's viewWillAppear method I set the tint color back to nil so that it's the default color again. The navigation bar looks as expected. However if I push the view controller on the stack yet again, the navigation bar's tint color is pink, but the back button's color is the default light blue.
Hope that was understandable.</p>

<p>So what's the cause of the problem?</p>
