title: Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value while applying effects to image
body: <p>I am trying to apply slide, fade and grow effect to my imageview.
  Following is my code  </p>
  
  <pre><code>@IBAction func fadeIn(_ sender: Any) {
      imageView.alpha=0
      UIView.animate(withDuration: 1, animations: {
          self.imageView.alpha=1
      })
  }
  
  @IBAction func slideIn(_ sender: Any) {
      imageView.center=CGPoint(x:imageView.center.x-500,y:imageView.center.y)
      UIView.animate(withDuration: 2) {
          self.imageView.center=CGPoint(x:self.imageView.center.x+500,y:self.imageView.center.y)
      }
  
  }
  
  @IBAction func grow(_ sender: Any) {
      imageView.frame=CGRect(x:0,y:0,width:0,height:0)
      UIView.animate(withDuration: 1, animations: {
          self.imageView.frame=CGRect(x:0,y:0,width:200,height:200)
      })
  }
  </code></pre>
  
  <p>Whenever i click on any of the button i get </p>
  
  <pre><code>Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
  </code></pre>
  
  <p>Any help would be greatly appreciated.</p>