title: UIPopoverController size changes when new controller is push on navigation controller set in UIPopover controller
body: <p>I have below issue with <code>UIPopoverController</code> and <code>UINavigationController</code>:</p>
  
  <p>I have created one <code>UINavigationController</code> with one <code>UITableViewController</code> in that. Then I have set this <code>UINavigationController</code> to <code>UIPopoverController</code>.<br>I have requirement to have square <code>UIPopoverController</code> so I used <code>setPopoverContentSize</code> of <code>UIPopoverController</code>. I also used <code>contentSizeForViewInPopover</code>.</p>
  
  <p>Issue is when I launch popover it is shown rectangle. But now when I push another <code>UITableViewController</code> by clicking on first <code>UITableViewController</code> row then whole popover is displayed with default size what normally we get.</p>
  
  <p>Please let me know how to overcome this issue.<br>
  If more detail is required then let me know.</p>