title: UISearchController searchBar in tableHeaderView animating out of the screen
body: <p>I have a <code>UISearchController</code> with a <code>UITableViewController</code> as a <code>searchResultsController</code>, the <code>UISearchBar</code> of this <code>searchController</code> is set to be in the <code>tableHeaderView</code> of my current <code>tableView</code> displayed in my root ViewController. Almost everything is working well, as expected. But in the animation of the <code>UISearchBar</code> (When i click on the searchBar and the <code>UINavigationBar</code> hides and the searchBar goes to the top, as in the <code>UISearchDisplayController</code>) i have a strange behavior. Instead of moving to the position of the <code>UINavigationBar</code> (y: 0), it jumps out of the screen and than starts the animation that shows the cancel button. I tried moving my instantiate code to the <code>viewDidLoad</code> instead of <code>init</code>, and the things are just the same. I think that the center of the problem is in the frame of the <code>searchResultsController</code>'s view, but i'm not sure about that(I tried setting the frame, without success). Everything that i am doing is in pure code.</p>
  
  <p>Here is the relevant part of the code:</p>
  
  <pre><code>- (void) viewDidLoad { 
      [super viewDidLoad];
  
      // search controller setup
      self.searchController = [[UISearchController alloc] initWithSearchResultsController:self.searchResultsController];
      self.searchController.delegate = self;
      self.searchController.searchResultsUpdater = self;
      self.searchController.searchBar.delegate = self;
  
      [self.searchController.searchBar sizeToFit];
      self.tableView.tableHeaderView = self.searchController.searchBar;
  
      self.searchController.definesPresentationContext = YES;
  }
  </code></pre>
  
  <p>And i have a lazy load for the <code>searchResultsController</code>:</p>
  
  <pre><code>- (UITableViewController *)searchResultsController {
      if (_searchResultsController == nil) {
          _searchResultsController = [[UITableViewController alloc] initWithStyle:UITableViewStylePlain];
          _searchResultsController.tableView.delegate = self;
          _searchResultsController.tableView.dataSource = self;
      }
      return _searchResultsController;
  }
  </code></pre>
  
  <p>I've downloaded the sample code from apple, but they use storyBoards and a xib for UITableViewCell, the SearchController works perfectly in the project. Does anyone had the same problem? How can i fix this? Any solutions or suggestions would be appreciated.</p>
  
  <p>Thanks for the attention.</p>