title: Application crash when set header of UICollectionView horizontally
body: <p>I am pretty new in UICollectionView. And I am really tired to find out the solution. I am trying to add Header in 3 Horizontally Row. I am using Collection view flow layout.<br>
  Here is my code which I implement:  </p>
  
  <pre><code>    - (void)awakeFromNib {
  
      self.collectionView.backgroundColor = [UIColor colorWithRed:204.0/255.0 green:204.0/255.0 blue:204.0/255.0 alpha:1.0];
  
      self.collectionView.backgroundColor = [UIColor clearColor];
      self.collectionView.backgroundView = [[UIView alloc] initWithFrame:CGRectZero];
      UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
      flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
      flowLayout.itemSize = CGSizeMake(130.0, 170.0);
      [self.collectionView setCollectionViewLayout:flowLayout];
  
      // Register the colleciton cell
      [_collectionView registerNib:[UINib nibWithNibName:@"ORGArticleCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"ORGArticleCollectionViewCell"];
      [self.collectionView registerClass:[_HeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView"];
  }
  #pragma mark - UICollectionViewDataSource methods
  - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
      return 1;
  }
  
  - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
      if (section == 0) {
          return [self.collectionData count];
      }
      else if(section == 1)
      {
          return [self.collectionData1 count];
      }
      else
      {
          return [self.collectionData2 count];
      }
  }
  
  - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {
      ORGArticleCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ORGArticleCollectionViewCell" forIndexPath:indexPath];
  
      cell.articleTitle.text = [self.collectionData objectAtIndex:[indexPath row]];
      NSString *URL = [self.collectionImageData objectAtIndex:indexPath.row];
      [cell.articleImage setImageWithURL:[NSURL URLWithString:URL] placeholderImage:[UIImage imageNamed:@"profile-image-placeholder"]];
      cell.articleImage.contentMode = UIViewContentModeScaleToFill;
      cell.articlePrice.text = [self.collectionDataPric objectAtIndex:[indexPath row]];
      return cell;
  }
  
  - (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
  {
      NSDictionary *cellData = [self.collectionData objectAtIndex:[indexPath row]];
      [[NSNotificationCenter defaultCenter] postNotificationName:@"didSelectItemFromCollectionView" object:cellData];
  }
  - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
  {
      return 0;
  }
  
  - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
  {
      return 0;
  }
  - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
  
      UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:
                                              UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath];
      UILabel *label = (UILabel *)[headerView viewWithTag:10];
      if (!label) {
          label = [[UILabel alloc] initWithFrame:CGRectInset(headerView.bounds, 5, 5)];
          label.tag = 10;
          label.font = [UIFont boldSystemFontOfSize:12];
          label.textColor = [UIColor darkGrayColor];
          [headerView addSubview:label];
      }
  
      label.text = [NSString stringWithFormat:@"Section %d", indexPath.section];
      return headerView;
  }
  
  - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section {
      CGSize headerSize = CGSizeMake(320, 44);
      return headerSize;
  }
  </code></pre>
  
  <p>My App crash in viewForSupplementaryElementOfKind method when I initialize the header view.<br>
  Following are the crash log:  </p>
  
  <blockquote>
    <p>Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForSupplementaryElementOfKind: UICollectionElementKindSectionHeader at path  {length = 2, path = 0 - 0}'</p>
  </blockquote>