title: Swift2 retrieving images from Firebase
body: <p>I am trying to read/display an image from Firebase. I am first encoding the image and then posting this encoded String to Firebase. This runs fine. When I try and decode the encoded string from Firebase and convert it to an image, I am getting a nil value exception.</p>
  
  <p>This is how I am saving the image to Firebase</p>
  
  <pre><code>var base64String: NSString!
  func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {
  
      self.dismissViewControllerAnimated(true, completion: nil)
  
      imageToPost.image = image
  
      var uploadImage = image as! UIImage
      var imageData = UIImagePNGRepresentation(uploadImage)!
      self.base64String = imageData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)
      let ref = Firebase(url: "https://XXX.firebaseio.com")
  
      var quoteString = ["string": self.base64String]
      var usersRef = ref.childByAppendingPath("goalImages")
      var users = ["image": quoteString]
      usersRef.setValue(users)
  
      displayAlert("Image Posted", message: "Your image has been successfully posted!")
  }
  </code></pre>
  
  <p>This is how I am trying to read the image from Firebase</p>
  
  <pre><code>//  ViewController.swift
  
  import UIKit
  import Firebase
  
  class ViewController: UIViewController {
  @IBOutlet weak var image: UIImageView!
  var base64String: NSString!
  
  @IBAction func buttonClicked(sender: AnyObject) {
  
      sender.setTitle("\(sender.tag)", forState: UIControlState.Normal)
  
  }
  
  override func viewDidLoad() {
      super.viewDidLoad()
      // Do any additional setup after loading the view, typically from a nib.
  
      let ref = Firebase(url: "https://XXX.firebaseio.com/goalImages/image/string")
  
      ref.observeEventType(.Value, withBlock: { snapshot in
  
          self.base64String = snapshot.value as! NSString
          let decodedData = NSData(base64EncodedString: self.base64String as String, options: NSDataBase64DecodingOptions())
          //Next line is giving the error
          var decodedImage = UIImage(data: decodedData!)
  
          self.image.image = decodedImage
          }, withCancelBlock: { error in
              print(error.description)
          })
  
  }
  
  override func didReceiveMemoryWarning() {
      super.didReceiveMemoryWarning()
      // Dispose of any resources that can be recreated.
  }
  }
  </code></pre>
  
  <p>The error says: "fatal error: unexpectedly found nil while unwrapping an Optional value"; decodedData is nil. Could someone explain what is going wrong. </p>