title: [UIDevice currentDevice].identifierForVendor.UUIDString returns all zeros
body: <p>I have iPhone 4 with iOS 6.0 .
  <br>This property</p>
  
  <pre><code>[UIDevice currentDevice].identifierForVendor.UUIDString 
  </code></pre>
  
  <p>always returning the all zeros ( 00000-----) . 
  <br>Help me to fix this issue.
  <br>I have searched in the google.
  <br>I did the restart,deleted the app ... . But no use . </p>