title: Having issue calling delegate method and updating UI in the previous view controller
body: <p>I want to use a delegate method to update some UI in my top view controller from the current view controller. I'm getting error <code>unexpectedly found nil while unwrapping an Optional value</code>. Please have a look at the following code and suggest what's wrong.</p>
  
  <p><img src="https://i.stack.imgur.com/3dUGp.png" alt="First View Controller"></p>
  
  <p><img src="https://i.stack.imgur.com/lRGwn.png" alt="Second View Controller"></p>