【Swift4】UIImageView must be used from main thread only と動作拒否されたので対応

extension UIImageView {
  func loadImageAsynchronously(url: String?, defaultUIImage: UIImage? = nil) -> Void {
    if url == nil {
      self.image = defaultUIImage
      return
    }
    DispatchQueue.global().async {
      do {
        PINCache.shared().object(forKey: url!) { (cache, key, object) in
          if let image = object as? UIImage {
            DispatchQueue.main.async {
              self.image = image
            }
          }else{
            let storage = Storage.storage().reference().child(url!)
            storage.getData(maxSize: 1 * 1024 * 1024) { data, error in
              if let error = error {
                // Uh-oh, an error occurred!
              } else {
                // Data for "images/island.jpg" is returned
                let image = UIImage(data: data!)!
                PINCache.shared().setObject(image, forKey: url!)
                DispatchQueue.main.async {
                  self.image = image
                }
              }
            }
          }
        }
      }
      catch {
        DispatchQueue.main.async {
          self.image = defaultUIImage
        }
      }
    }
  }
}