title: when i start the app i see a white screen and tells me this error, how can i fix it?
body: <p>when i start the app i see a white screen and tells me this error, how can i fix it? the error appears in this line: </p>
  
  <p>![myLabel.alpha = 0]</p>
  
  <p>the error is Thread 1: EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP,subcode0x0)</p>
  
  <pre><code>import UIKit
  
  class ViewController: UIViewController {
  
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
            myLabel.alpha = 0
      }
  
      override func didReceiveMemoryWarning() {
          super.didReceiveMemoryWarning()
          // Dispose of any resources that can be recreated.
      }
  </code></pre>