My playlist browser app crashes because of two lines

@IBOutlet weak var aButton: UIButton!
@IBOutlet weak var playlistImageView0: UIImageView!


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    aButton.setTitle("Press Me", forState: .Normal)

    let playlist = Playlist(index: 0)
    playlistImageView0.image = playlist.icon
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showPlaylistDetail" {
        let playlistDetailController = segue.destinationViewController as PlaylistDetailViewController
        playlistDetailController.playlist = Playlist(index: 0)
    }
}

var title: String?
var description: String?
var icon: UIImage?
var largeIcon: UIImage?
var artists: [String] = []
var backgroundColor:UIColor = UIColor.clearColor()

init(index: Int) {
    let musicLibrary = MusicLibrary().library
    let playlistDictionary = musicLibrary[index]

    title = playlistDictionary["title"] as String!
    description = playlistDictionary["description"] as String!

    let iconName = playlistDictionary["icon"] as String!
    icon = UIImage(named: iconName)
    let largeIconName = playlistDictionary["largeIcon"] as String
    largeIcon = UIImage(named: largeIconName)

    artists += playlistDictionary["artists"] as [String]

    let colorsDictionary = playlistDictionary["backgroundColor"] as [String: CGFloat]
    backgroundColor = rgbColorFromDictionary(colorsDictionary)


}

func rgbColorFromDictionary(colorDictionary: [String: CGFloat]) -> UIColor {
    let red = colorDictionary["red"]!
    let green = colorDictionary["green"]!
    let blue = colorDictionary["blue"]!
    let alpha = colorDictionary["alpha"]!

    return UIColor(red: red/255.0, green: green/255.0, blue: blue/255.0, alpha: alpha/255.0)
}

var playlist: Playlist?

@IBOutlet weak var playlistTitle: UILabel!
@IBOutlet weak var playlistDescription: UILabel!
@IBOutlet weak var playlistCoverImage: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    if playlist != nil {
        playlistCoverImage.image = playlist!.largeIcon
        playlistCoverImage.backgroundColor = playlist!.backgroundColor

        playlistTitle.text = playlist!.title 
        playlistDescription.text = playlist!.description 

    }




}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}