title: Why is my system image not showed in my app at runtime?
body: <p>I am using Xcode 11, swift 4 and iOs 11.4
  With the latest 11.0 Xcode version, we now have possibility to use native system icons (finally..)</p>
  
  <p>I created a button with a system image, the "+". It does appears in my instantBuilder Xcode but when I run my app, the button is visible, but not the image</p>
  
  <p><a href="https://i.stack.imgur.com/EOHjR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EOHjR.png" alt="list image"></a>
  <a href="https://i.stack.imgur.com/kx0OA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kx0OA.png" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/4zv5s.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4zv5s.png" alt="![runtime view"></a></p>
  
  <p>Any idea what I might have done bad ? </p>