title: UITableView -headerViewForSection returns (null)
body: <p>I have a <code>UITableView</code> with 2 sections. Each with it's own <code>headerView</code>.<br>
  I have created a custom <code>headerView</code> via the <code>-viewForHeaderInSection:</code> method.<br>
  Later, I plan to modify it a bit so I need to use the <code>viewForHeader</code> method but I am unable to access the <code>headerView</code> and it's <code>subViews</code>.</p>
  
  <p>As a simple example, I'm trying to <code>NSLog</code> the <code>viewForHeader</code> object in the <code>-didSelectRowAtIndexPath:</code> but I get a <code>(null)</code> result.</p>
  
  <p>Sample Code:  </p>
  
  <pre><code>-(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
  {
      return 75;
  }
  
  -(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
  {    
      UIView *myHeader = [[UIView alloc] init];
      switch (section) {
          case 0:
              [myHeader setBackgroundColor:[UIColor greenColor]];
              break;
          case 1:
              [myHeader setBackgroundColor:[UIColor redColor]];
              break;
          default:
              break;
      }
  
      UILabel *myLabel = [[UILabel alloc] init];
      [myLabel setFrame:CGRectMake(10, 0, 100, 30)];
      [myLabel setTag:101];
      [myLabel setBackgroundColor:[UIColor clearColor]];
      [myLabel setText:[NSString stringWithFormat:@"Section: %d",section]];
  
      [myHeader addSubview:myLabel];    
      return myHeader;
  }
  
  - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
  {
      UITableViewHeaderFooterView *testView = [self.tableView headerViewForSection:indexPath.section];
      NSLog(@"%@",testView);  //displays (null)
  }
  </code></pre>
  
  <hr>
  
  <p>Do I need to create the custom <code>UIView</code> xib as the <code>headerView</code>? (<em>because as per a <a href="https://stackoverflow.com/questions/15231726/uitableview-headerviewforsection-always-returns-nil">similar question</a> and as per the docs</em>")</p>
  
  <blockquote>
    <p>To make the table view aware of your header or footer view, you need to register it.<br>
    You do this using the registerNib:forCellReuseIdentifier: or<br>
    registerClass:forCellReuseIdentifier: method of UITableView.</p>
  </blockquote>