             }
         }
         
-        navigationItem.rightBarButtonItem = actionButton!
+        navigationItem.rightBarButtonItem = actionButton
         
         let numberOfPages = CGFloat(document.pageCount)
         let cellSpacing = CGFloat(2.0)

    
    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "page", for: indexPath) as! PDFPageCollectionViewCell
        cell.setup((indexPath as NSIndexPath).row, collectionViewBounds: collectionView.bounds, document: document, pageCollectionViewCellDelegate: self)
        return cell
    }
}

    
    override public func viewDidLoad() {
        super.viewDidLoad()
        collectionView?.register(PDFPageCollectionViewCell.self, forCellWithReuseIdentifier: "page")
        
        if actionButton == nil {
            if let actionButtonImage = actionButtonImage {
