fix: avoid crashing from nil values

ImageViewer/ViewController.swift

@@ -124,15 +124,17 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
         if let alert = pendingAlert {
             present(alert, animated: false, completion: nil)
         }
-        if !hasSetContentOffset, let scrollPos = state[currentPath.lastPathComponent]?.scrollPos {
+        if !hasSetContentOffset && scrollingCollectionView != nil {
+            guard let path = currentPath else { return }
+            guard let state = state[path.lastPathComponent] else { return }
             let screenSize = UIScreen.main.bounds.size
-            var offset = scrollPos
+            var offset = state.scrollPos
             if screenSize.width > screenSize.height {
                 offset.y *= (screenSize.width / screenSize.height)
             }
             scrollingCollectionView.setContentOffset(offset, animated: false)
             hasSetContentOffset = true
-        } else {
+        } else if scrollingCollectionView != nil {
             let screenSize = UIScreen.main.bounds.size
             var offset = scrollingCollectionView.contentOffset
             offset.y *= (screenSize.width / screenSize.height)
@@ -268,8 +270,8 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
                 && isDirectory.boolValue
         }.sorted { $0.path < $1.path }
 
-        for dir in directories {
-            queue.async { [self] in
+        queue.async { [self] in
+            for dir in directories {
                 if !fileManager.fileExists(atPath: dir.appendingPathComponent(metadataFilename).path) {
                     getMetadataFromFilename(path: dir)
                     if pendingAlert != nil {
@@ -885,6 +887,7 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
     override func viewDidLayoutSubviews() {
         super.viewDidLayoutSubviews()
         guard view.bounds.size != lastLayoutSize else { return }
+        if scrollingCollectionView == nil { return }
         lastLayoutSize = UIScreen.main.bounds.size
         if scrollingCollectionView.isHidden
             || getMode() != .scroll