The VendingMachine app keeps crashing after completing the finishing touches video any help?

init(inventory: [VendingSelection: ItemType])
func vend(selection: VendingSelection, quantity: Double) throws
func deposit(amount: Double)

    guard let path = NSBundle.mainBundle().pathForResource(resource, ofType: type) else {
        throw InventoryError.InvalidResource
    }

    guard let dictionary = NSDictionary(contentsOfFile: path),
    let castDictionary = dictionary as? [String: AnyObject] else {
        throw InventoryError.ConversionError
    }

    return castDictionary
}

    var inventory: [VendingSelection: ItemType] = [:]

    for (key, value) in dictionary {
        if let itemDict = value as? [String : Double], let price = itemDict["price"], let quantity = itemDict["quantity"] {

            let item = VendingItem(price: price, quantity: quantity)

            guard let key = VendingSelection(rawValue: key) else {
                throw InventoryError.InvalidKey
            }

            inventory.updateValue(item, forKey: key)
        }
    }

    return inventory

}

let selection: [VendingSelection] = [.Soda, .DietSoda, .Chips, .Cookie, .Sandwich, .Wrap, .CandyBar, .PopTart, .Water, .FruitJuice, .SportsDrink, .Gum]
var inventory: [VendingSelection: ItemType]
var amountDeposited: Double = 10.0

required init(inventory: [VendingSelection : ItemType]) {
    self.inventory = inventory
}
func vend(selection: VendingSelection, quantity: Double) throws {
    // add code
}
func deposit(amount: Double) {
    // add code
}

@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var totalLabel: UILabel!
@IBOutlet weak var balanceLabel: UILabel!
@IBOutlet weak var quantityLabel: UILabel!

let vendingMachine: VendingMachineType

required init?(coder aDecoder: NSCoder) {
    do {
        let dictionary = try PlistConverter.dictionaryFromFile("VendingInventory", ofType: "plist")
        let inventory = try InventoryUnarchiver.vendingInventoryFromDictionary(dictionary)
        self.vendingMachine = VendingMachine(inventory: inventory)
    } catch let error {
        fatalError("\(error)")
    }
    super.init(coder: aDecoder)
}

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

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

// MARK: - UICollectionView 

func setupCollectionViewCells() {
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)
    let padding: CGFloat = 10
    layout.itemSize = CGSize(width: (screenWidth / 3) - padding, height: (screenWidth / 3) - padding)
    layout.minimumInteritemSpacing = 10
    layout.minimumLineSpacing = 10

    collectionView.collectionViewLayout = layout
}

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return vendingMachine.selection.count
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! VendingItemCell

    return cell
}

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: true)

}

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: false)
}

func collectionView(collectionView: UICollectionView, didHighlightItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: true)
}

func collectionView(collectionView: UICollectionView, didUnhighlightItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: false)
}

func updateCellBackgroundColor(indexPath: NSIndexPath, selected: Bool) {
    if let cell = collectionView.cellForItemAtIndexPath(indexPath) {
        cell.contentView.backgroundColor = selected ? UIColor(red: 41/255.0, green: 211/255.0, blue: 241/255.0, alpha: 1.0) : UIColor.clearColor()
    }
}

// MARK: - Helper Methods