title: iOS 11 - Keyboard Height is returning 0 in keyboard notification
body: <p>I have been using Keyboard notifications without any problem and getting exact height of Keyboard.</p>
  
  <pre><code>- (void)keyboardDidShow:(NSNotification *) notification{
      CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
  
      NSLog(@"%f",keyboardSize.height);}
  </code></pre>
  
  <p>but with iOS 11 the size of keyboard is 0 when the notification is called. </p>
  
  <p>What is the problem occurring in this scenario? I am using xcode 9 Beta 5</p>