refactor: use auto-released notification observer api

src/logic/events/SpacesEvents.swift

@@ -2,10 +2,10 @@ import Cocoa
 
 class SpacesEvents {
     static func observe() {
-        NSWorkspace.shared.notificationCenter.addObserver(forName: NSWorkspace.activeSpaceDidChangeNotification, object: nil, queue: nil, using: handleEvent)
+        NSWorkspace.shared.notificationCenter.addObserver(self, selector: #selector(handleEvent), name: NSWorkspace.activeSpaceDidChangeNotification, object: nil)
     }
 
-    private static func handleEvent(_ notification: Notification) {
+    @objc private static func handleEvent(_ notification: Notification) {
         Logger.debug(notification.name.rawValue)
         // if UI was kept open during Space transition, the Spaces may be obsolete; we refresh them
         Spaces.refreshSpacesAndWindows()

src/ui/main-window/ThumbnailsView.swift

@@ -258,12 +258,16 @@ class ScrollView: NSScrollView {
     }
 
     private func observeScrollingEvents() {
-        NotificationCenter.default.addObserver(forName: NSScrollView.didEndLiveScrollNotification, object: nil, queue: nil) { [weak self] _ in
-            self?.isCurrentlyScrolling = false
-        }
-        NotificationCenter.default.addObserver(forName: NSScrollView.willStartLiveScrollNotification, object: nil, queue: nil) { [weak self] _ in
-            self?.isCurrentlyScrolling = true
-        }
+        NotificationCenter.default.addObserver(self, selector: #selector(scrollingStarted), name: NSScrollView.willStartLiveScrollNotification, object: nil)
+        NotificationCenter.default.addObserver(self, selector: #selector(scrollingEnded), name: NSScrollView.didEndLiveScrollNotification, object: nil)
+    }
+
+    @objc private func scrollingStarted() {
+        isCurrentlyScrolling = true
+    }
+
+    @objc private func scrollingEnded() {
+        isCurrentlyScrolling = false
     }
 
     private func resetHoveredWindow() {