     // MARK: - Actions
 
     @IBAction func handleButtonAction(_ sender: FormatBarItem) {
-        formatter?.handleActionForIdentifier(sender.identifier!)
+        guard let identifier = sender.identifier else { return }
+
+        formatter?.handleActionForIdentifier(identifier)
     }
 
     @IBAction func handleToggleButtonAction(_ sender: FormatBarItem) {


    struct Constants {
        static let fixedSeparatorMidPointPaddingX = CGFloat(5)
        static let fixedStackViewInsets = UIEdgeInsets(top: 0, left: 15, bottom: 0, right: 10)
        static let scrollableStackViewInsets = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
        static let stackViewCompactSpacing = CGFloat(0)
        static let stackViewRegularSpacing = CGFloat(0)
        static let stackButtonWidth = CGFloat(44)

    ///
    open var overflowItems = [FormatBarItem]() {
        didSet {
            configure(items: overflowItems)

            let hasOverflowItems = !overflowItems.isEmpty
            setOverflowToggleItemVisible(hasOverflowItems)
        }
