     
     // MARK: Private Properties
     
-    private var occlusionStateObserver: NSKeyValueObservation?
-    
     @IBOutlet private weak var splitViewItem: NSSplitViewItem?
     @IBOutlet private weak var statusBarItem: NSSplitViewItem?
     
     
     
     // MARK: -
-    // MARK: Lifecycle
-    
-    deinit {
-        self.occlusionStateObserver?.invalidate()
-    }
-    
-    
-    
     // MARK: Split View Controller Methods
     
     override func viewDidLoad() {

            let indicator = ProgressViewController(progress: progress, message: message, closesWhenFinished: true)
            
            self?.presentViewControllerAsSheet(indicator)
        }
    }
    

        let threshold = UserDefaults.standard[.showColoringIndicatorTextLength]
        guard threshold > 0, highlightLength > threshold else { return }
        
        guard let window = self.view.window else {
            assertionFailure("Expeced window to be non-nil.")
            return
        }
        
        // display indicator first when window is visible
        let presentBlock = { [weak self, weak progress] in
            guard
                let progress = progress,
                !progress.isFinished, !progress.isCancelled
