title: SDWebImage do not assign an image from url - Downloaded image has 0 pixels
body: <p>This is my simple extension for <code>UIImageView</code>:</p>
  
  <pre><code>extension UIImageView {
  
  func setImageWithUrl(url: String?) {
      setImageWithUrl(url, placeholder: nil)
  }
  
  private func setImageWithUrl(url: String?, placeholder: UIImage? = UIImage(), deleteCacheImage: Bool = false) {
  
      image = placeholder ?? image
  
      if let url = url {
  
          let activityIndicatorView = UIActivityIndicatorView(frame: CGRectMake(0, 0, CGRectGetWidth(frame), CGRectGetHeight(frame)))
          activityIndicatorView.hidden = false
          activityIndicatorView.color = UIColor.curiousBlue()
  
          addSubview(activityIndicatorView)
          bringSubviewToFront(activityIndicatorView)
  
          activityIndicatorView.startAnimating()
  
          let options = deleteCacheImage ? SDWebImageOptions.RefreshCached : SDWebImageOptions.LowPriority
  
          sd_setImageWithURL(NSURL(string: url), placeholderImage: placeholder, options: options, completed: { image, error, cache, url in
  
              activityIndicatorView.hidden = true
              activityIndicatorView.stopAnimating()
              activityIndicatorView.removeFromSuperview()
          })
      }
  }
  }
  </code></pre>
  
  <p>Example <a href="http://posbistro-prod.s3.amazonaws.com/user_images/images/245/45d/c7-/medium/user_image20150728-25823-hapq90.png" rel="noreferrer">image</a>.</p>
  
  <p>but <code>image</code> in block is <code>nil</code>. Why? It returns an error: </p>
  
  <blockquote>
    <p>Downloaded image has 0 pixels</p>
  </blockquote>
  
  <p>I have the latest version of <code>SDWebImage</code>, through cocoapods: <strong>3.7.5</strong>.</p>