title: create an empty section(header view) with no cell in core data
body: <p>I have two entities. user and attributes. user has a one-to-one relationship to attributes and attribute has one-to-many relationship to the user.
  i am using FRC(Fetch result controller and want to use 'user' entity as section( header view) and attributes as table view cell. 
  I want to be able to add a user section(header view) with no cell.
  but as default I get one cell per new section.</p>
  
  <p>here is the code for FRC :</p>
  
  <pre class="lang-swift prettyprint-override"><code> lazy var fetchResultController: NSFetchedResultsController&lt;Attribute&gt; = {
          let fetchRequest: NSFetchRequest&lt;Attribute&gt; = Attribute.fetchRequest()
          fetchRequest.sortDescriptors = [NSSortDescriptor(key: #keyPath(Attribute.name), ascending: false)]
  
          let fetchResultController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.persistentContainer.managedContext, sectionNameKeyPath: #keyPath(Attribute.user.name), cacheName: nil)
  
          fetchResultController.delegate = self
  
          return fetchResultController
      }()
  </code></pre>
  
  <p>tableView: </p>
  
  <pre class="lang-swift prettyprint-override"><code>func numberOfSections(in tableView: UITableView) -&gt; Int {
          guard let sections = fetchResultController.sections else {return 0}
          return sections.count
      }
  
      func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -&gt; Int {
          guard let section = fetchResultController.sections?[section] else{return 0}
          return section
  
      }
      func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -&gt; UITableViewCell {
          let cell = tableView.dequeueReusableCell(withIdentifier: ID.TableView.mainPage) as! AttributeCell
          let task = fetchResultController.object(at: indexPath)
  
          cell.nameLbl.text = task.name
  
          return cell
      }
  </code></pre>