title: Strange behavior of MPMusicPlayerController.currentPlaybackTime
body: <p>While a song is being played, I tried to get currentPlaybackTime.</p>
  
  <pre><code>        NSLog(@"Playback: %f", appDelegate.appMusicPlayer.currentPlaybackTime);
  </code></pre>
  
  <p>I always got "Playback: nan". The application gets the currentPlaybackTime correctly when running (not debugging). The LLDB debugger also gives the correct currentPlaybackTime.</p>
  
  <p>Does anyone know what going on with this property?</p>