title: Parse Link/Unlink user completion blocks never called (Twitter/Facebook)
body: <p>I am trying to add link/unlink functionality for both Twitter and Facebook via the Parse iOS SDK but I am having an issue I've never encountered before - the completion blocks for link and unlink user are never being called. The following is the code I am using for link / unlink functionality and I was wondering if anyone has encountered something similar before and might have any ideas as to what the problem is. Thanks</p>
  
  <pre><code>@IBAction func atnFacebookConnect(sender: AnyObject) {
      disableUserInteraction()
      self.actFacebookConnect.startAnimating()
      let permissions = ["email","public_profile","user_about_me"]
      if btnFacebookConnect.titleLabel?.text == "Disconnect" {
          if let user = User.currentUser() {
              PFFacebookUtils.unlinkUserInBackground(user, block: { (success, error) -&gt; Void in
                  if error == nil &amp;&amp; success == true {
                      self.checkIfUserIsLinkedToSocialMedia()
                  }
                  else {
                      iLikeyAlert(self, "", "Something went wrong", nil)
                  }
                  self.actFacebookConnect.stopAnimating()
                  self.enableUserInteraction()
              })
          }
      }
      else if btnFacebookConnect.titleLabel?.text == "Connect" {
          if let user = User.currentUser() {
              PFFacebookUtils.linkUserInBackground(user, withReadPermissions:permissions, block: { (success, error) -&gt; Void in
                  if error == nil &amp;&amp; success == true {
                      self.checkIfUserIsLinkedToSocialMedia()
                  }
                  else {
                      iLikeyAlert(self, "", "Something went wrong", nil)
                  }
                  self.actFacebookConnect.stopAnimating()
                  self.enableUserInteraction()
              })
          }
      }
  }
  
  @IBAction func atnTwitterConnect(sender: AnyObject) {
      disableUserInteraction()
      self.actTwitterConnect.startAnimating()
      if btnTwitterConnect.titleLabel?.text == "Disconnect" {
          if let user = User.currentUser() {
              PFTwitterUtils.unlinkUserInBackground(user, block: { (success, error) -&gt; Void in
                  if error == nil &amp;&amp; success == true {
                      self.checkIfUserIsLinkedToSocialMedia()
                  }
                  else {
                      iLikeyAlert(self, "", "Something went wrong", nil)
                  }
                  self.actTwitterConnect.stopAnimating()
                  self.enableUserInteraction()
              })
          }
      }
      else if btnTwitterConnect.titleLabel?.text == "Connect" {
          if let user = User.currentUser() {
              PFTwitterUtils.linkUser(user, block: { (success, error) -&gt; Void in
                  if error == nil &amp;&amp; success == true {
                      self.checkIfUserIsLinkedToSocialMedia()
                  }
                  else {
                      iLikeyAlert(self, "", "Something went wrong", nil)
                  }
                  self.actTwitterConnect.stopAnimating()
                  self.enableUserInteraction()
              })
          }
      }
  }
  </code></pre>