title: Firebase sign out not working in Swift
body: <p>I am using newest Firebase API (3.2.1) and I am using this code to check if user is signed in:</p>
  
  <pre><code>override func viewDidAppear(animated: Bool) {
      super.viewDidAppear(animated)
  
      if(self.navigationController != nil){
          self.navigationController!.setNavigationBarHidden(true, animated: true)
      }
  
      if(FIRAuth.auth() != nil){
          self.performSegueWithIdentifier("loginSuccessSegue", sender: self)
      }
  }
  </code></pre>
  
  <p>In other words if auth object is present I am switching to other controller. On that controller I have sign out button which is doing sign out like this:</p>
  
  <pre><code>do{
      try FIRAuth.auth()?.signOut()
      self.performSegueWithIdentifier("logoutSegue", sender: self)
  }catch{
      print("Error while signing out!")
  }
  </code></pre>
  
  <p>I do not get error on this operation but when I am switched to login controller, this auth object is present and I get switched back again to controller with data. I also tried checking the current user object in auth and it is present and valid.</p>
  
  <p>Anyone knows how an I properly do sign out?</p>