title: Why DispatchQueue.main.async is not performed?
body: <p>My app has finished to respond unexpectedly. I have researched and noticed that this operator is never performed (see picture). Why? queue is nil. I use Xcode 8.1. In point "come here" I'm on the thread 3. So any request is not performed.
  <a href="https://i.stack.imgur.com/Oba6s.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Oba6s.png" alt="enter image description here"></a></p>
  
  <p><strong>Edit.</strong> Storyboard is loading at the same time. iOS can't load storyboard which I created in Xcode 7.3. Even it had been working for some time in Xcode 8. I don't know what happened and why it finished to work. I checked changes on git. They are absent. Probably I have to recreate my storyboard on Xcode 8.</p>