title: Initializer for conditional binding must have Optional type, not"()"
body: <p>I couldn't solve an "if let" issue in my code. Based on the error it says that I must use an optional type? </p>
  
  <pre><code>@IBAction func operate(sender: UIButton) {
  
      if userIsInTheMiddleOfTypingANumber{
          enter()
      }
      if let operation = sender.currentTitle {
          if let result = calcModel.performOperation(operation){
              displayValue = result
          }else {
              displayValue = 0
          }
      }
  }
  </code></pre>