set self.navigationItem.rightBarButtonItem background image cause crash
<p>I used the codes below to set the background image of self.navigationItem.rightBarButtonItem</p>

<pre><code>[self.navigationItem.rightBarButtonItem 
                     setBackgroundImage: [UIImage imageNamed:@"top_button.png"]
                     forState:UIControlStateNormal 
                     barMetrics:UIBarMetricsDefault];
</code></pre>

<p>it will cause crash, </p>

<p>I used Xcode 4.3, deploy target 4.0, iPhone os 4.3.3</p>

<p>It worked well on simulator 5.1, but crashed on device</p>

<p>Welcome any comment</p>
