Receiving a fatal error when running app "Fatal error - array index out of range"

import Foundation
import UIKit


struct Playlist {


    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]  // the error is thrown on this line

        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)
    }