title: Disable supplementary view
body: <p>What is the correct of of disabling the supplementary views (e.g. header)? One time I want to show them (iPhone) and one time I don't want to show them (iPad).</p>
  
  <p>The only idea I currently have is to return a size of zero in <code>referenceSizeForHeaderInSection</code>. But I think it's kind of an overhead to create views, which aren't used at all. On the other side I have to implement <code>collectionView:viewForSupplementaryElementOfKind:atIndexPath:</code> and I can't return <code>nil</code>, because the app crashes then.</p>
  
  <p>How can I disable the supplementary views in <code>UICollectionView</code>?</p>