title: AVAudioPlayer.playing crash
body: <p>So I have this save button and if I press it the current viewController dismisses and any sound that is playing should stop.</p>
  
  <p>But it crashes as soon as I press the save button. What is the mistake in my code?</p>
  
  <pre><code>@IBAction func save(sender: UIBarButtonItem) {
  
      audioStopPlaying()
      dismissViewControllerAnimated(true, completion: nil)
  }
  
  func audioStopPlaying() {
      if model.audioPlayer.playing.boolValue == true {
          model.audioPlayer.stop()
  
      }
  }
  </code></pre>
  
  <p>Model:</p>
  
  <pre><code>class Model: NSObject {
  
      var audioPlayer: AVAudioPlayer = AVAudioPlayer()
  }
  </code></pre>