title: set height to 0 for header view of UITableView
body: <p>I used the code below to set the height of header view of UITableView</p>
  
  <pre><code>- (CGFloat)tableView:(UITableView *)tableView
  heightForHeaderInSection:(NSInteger)section
  {
      CGFloat height = 0.0; //  
  
      return height;
  }
  </code></pre>
  
  <p>but it display abnormal, shown as below</p>
  
  <p><img src="https://i.stack.imgur.com/7kv3n.png" alt="enter image description here"></p>
  
  <p>there is a white block, your comment welcome</p>