title: UISearchBar scope bar invisible in iOS7
body: <p>With the following code the scope bar is invisible (buttons work but are not visible - just black space)</p>
  
  <pre><code>UISearchBar* searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, self.tableView.frame.size.width, 44 + (_showScope?40:0));];
  searchBar.barStyle = UIBarStyleBlack;
  
  searchBar.scopeButtonTitles = [NSArray arrayWithObjects:@"string1", @"string2", nil];
  searchBar.showsScopeBar = YES;
  searchBar.delegate = self;
  
  self.tableView.tableHeaderView = searchBar;
  </code></pre>
  
  <p>works fine in iOS6.  Any ideas?</p>