Problem in Stormy app: My iconView is returning an nil error when I unwrap it (!)...

//
//  ViewController.swift
//  Stormy
//
//  Created by Christine Rose on 4/8/15.
//  Copyright (c) 2015 Christine Rose. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var iconView: UIImageView!
    @IBOutlet weak var currentTimeLabel: UILabel!
    @IBOutlet weak var temperatureLabel: UILabel!
    @IBOutlet weak var humidityLabel: UILabel!
    @IBOutlet weak var precipitatinLabel: UILabel!
    @IBOutlet weak var summaryLabel: UILabel!


    @IBOutlet weak var refreshButton: UIButton!
    @IBOutlet weak var refreshActivityIndicator: UIActivityIndicatorView!

    //keep API private via Access Controls
    private let apiKey = "e20b62c84b9c30a04d37bc81be771eb3"



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

        refreshActivityIndicator.hidden = true
        getCurrentWeatherData()


    }

    func getCurrentWeatherData() -> Void {

        let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/")
        let forecastURL = NSURL(string: "51.5072,-0.1275", relativeToURL: baseURL)

        let weatherData = NSData(contentsOfURL: forecastURL!, options: nil, error: nil)

        let sharedSession = NSURLSession.sharedSession() //singleton, global object, use sparingly

        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: { (location: NSURL!, response:NSURLResponse!, error: NSError!) -> Void in
            //this code might be causing a crash. Looks like this version is different than video

            if (error == nil) {
                let dataObject = NSData(contentsOfURL: location)

                let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject!, options: nil, error: nil) as! NSDictionary

                let currentWeather = Current(weatherDictionary: weatherDictionary)
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.temperatureLabel.text = "\(currentWeather.temperature)"
                    self.iconView.image = currentWeather.icon
                    self.currentTimeLabel.text = "At \(currentWeather.currentTime!) it is"
                    self.humidityLabel.text = "\(currentWeather.humidity)"
                    self.precipitatinLabel.text = "\(currentWeather.precipProbability)"
                    self.summaryLabel.text = "\(currentWeather.summary)"

                    //Stop refresh animation
                    self.refreshActivityIndicator.stopAnimating()
                    self.refreshActivityIndicator.hidden = true
                    self.refreshButton.hidden = false

                })


            } 


        })

        downloadTask.resume()

    }



    @IBAction func refresh() {

        getCurrentWeatherData()

        refreshButton.hidden = true
        refreshActivityIndicator.hidden = false
        refreshActivityIndicator.startAnimating()

    }

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


}

//
//  Current.swift
//  Stormy
//
//  Created by Christine Rose on 4/10/15.
//  Copyright (c) 2015 Christine Rose. All rights reserved.
//

import Foundation
import UIKit


struct Current {
    var currentTime: String?
    var temperature: Int
    var humidity: Double
    var precipProbability: Double
    var summary: String
    var icon: UIImage?

    init(weatherDictionary: NSDictionary) {
        let currentWeather = weatherDictionary["currently"] as! NSDictionary

        temperature = currentWeather["temperature"] as! Int
        humidity = currentWeather["humidity"] as! Double
        precipProbability = currentWeather["precipProbability"] as! Double
        summary = currentWeather["summary"] as! String


        let currentTimeIntValue = currentWeather["time"] as! Int
        currentTime = dateStringFromUnixtime(currentTimeIntValue)

        let iconString = currentWeather["icon"] as! String

    }

    func dateStringFromUnixtime(unixTime: Int) -> String {
        let timeInSeconds = NSTimeInterval(unixTime)
        let weatherDate = NSDate(timeIntervalSince1970: timeInSeconds)

        let dateFormatter = NSDateFormatter()
        dateFormatter.timeStyle = .ShortStyle

        return dateFormatter.stringFromDate(weatherDate)

    }

    func weaterIconFromString(stringIcon: String) -> UIImage {
        var imageName: String

        switch stringIcon {
            case "clear-day":
                imageName = "clear-day"
            case "clear-night":
                imageName = "clear-night"
            case "rain":
                imageName = "rain"
            case "snow":
                imageName = "snow"
            case "sleet":
                imageName = "sleet"
            case "wind":
                imageName = "wind"
            case "fog":
                imageName = "fog"
            case "cloudy":
                imageName = "cloudy"
            case "partly-cloudy-day":
                imageName = "partly-cloudy"
            case "partly-cloudy-night":
                imageName = "cloudy-night"
        default:
                imageName = "default"

        }
        var iconImage = UIImage(named: imageName)
        return iconImage!

    }



}