title: Set back view dark transparent when uimenu display
body: <p>When i try to add mask in background view where i displau UIMenu on UIButton click.
  UIMenu not get display.</p>
  <pre><code>self.view.mask = UIView(frame: self.view.frame)
  self.view.mask?.backgroundColor = UIColor.black.withAlphaComponent(0.2)
  self.view.mask?.isUserInteractionEnabled = false
  </code></pre>