fix: resolve analyzer warnings

- Fix empty catch block in track_provider.dart with comment
- Replace deprecated withOpacity() with withValues(alpha:) in library_settings_page.dart

lib/providers/track_provider.dart

@@ -556,7 +556,8 @@ class TrackNotifier extends Notifier<TrackState> {
       final tracks = List<Track>.from(state.tracks);
       tracks[index] = updatedTrack;
       state = state.copyWith(tracks: tracks);
-    } catch (e) {
+    } catch (_) {
+      // Silently ignore update failures - track may have been removed
     }
   }