title: Clear an optional variable in Swift
body: <p>If I declare an empty image:</p>
  
  <pre><code>var myImage: UIImage?
  </code></pre>
  
  <p>and then give it a value:</p>
  
  <pre><code>myImage = UIImage(named: "drawing.png")
  </code></pre>
  
  <p>how can I later remove that value, returning it to its original empty state?</p>