fix: local tracks getting fetched on first load

lib/components/library/user_local_tracks.dart

@@ -95,7 +95,7 @@ final localTracksProvider = FutureProvider<List<LocalTrack>>((ref) async {
             return {"metadata": metadata, "file": f, "art": imageFile.path};
           } catch (e, stack) {
             if (e is FfiException) {
-              return {};
+              return {"file": f};
             }
             Catcher.reportCheckedError(e, stack);
             return {};

lib/provider/proxy_playlist/proxy_playlist_provider.dart

@@ -22,7 +22,7 @@ import 'package:spotube/utils/type_conversion_utils.dart';
 /// Things to implement:
 /// * [x] Sponsor-Block skip
 /// * [x] Prefetch next track as [SpotubeTrack] on 80% of current track
-/// * [ ] Mixed Queue containing both [SpotubeTrack] and [LocalTrack]
+/// * [x] Mixed Queue containing both [SpotubeTrack] and [LocalTrack]
 /// * [ ] Modification of the Queue
 ///       * [x] Add track at the end
 ///       * [x] Add track at the beginning
@@ -218,6 +218,15 @@ class ProxyPlaylistNotifier extends PersistedStateNotifier<ProxyPlaylist>
     bool autoPlay = false,
   }) async {
     tracks = blacklist.filter(tracks).toList() as List<Track>;
+    final indexTrack = tracks.elementAtOrNull(initialIndex) ?? tracks.first;
+
+    if (indexTrack is LocalTrack) {
+      state = state.copyWith(
+        tracks: tracks.toSet(),
+        active: initialIndex,
+      );
+      await notificationService.addTrack(indexTrack);
+    } else {
       final addableTrack = await SpotubeTrack.fetchFromTrack(
         tracks.elementAtOrNull(initialIndex) ?? tracks.first,
         preferences,
@@ -228,19 +237,18 @@ class ProxyPlaylistNotifier extends PersistedStateNotifier<ProxyPlaylist>
         tracks: mergeTracks([addableTrack], tracks),
         active: initialIndex,
       );
-
       await notificationService.addTrack(addableTrack);
+      await storeTrack(
+        tracks.elementAt(initialIndex),
+        addableTrack,
+      );
+    }
 
     await audioPlayer.openPlaylist(
       state.tracks.map(makeAppropriateSource).toList(),
       initialIndex: initialIndex,
       autoPlay: autoPlay,
     );
-
-    await storeTrack(
-      tracks.elementAt(initialIndex),
-      addableTrack,
-    );
   }
 
   Future<void> jumpTo(int index) async {

lib/services/audio_services/linux_audio_service.dart

@@ -323,7 +323,7 @@ class _MprisMediaPlayer2Player extends DBusObject {
         "xesam:url": DBusString(
           playlist.activeTrack is SpotubeTrack
               ? (playlist.activeTrack as SpotubeTrack).ytUri
-              : playlist.activeTrack!.previewUrl!,
+              : playlist.activeTrack!.previewUrl ?? "",
         ),
         "xesam:genre": const DBusString("Unknown"),
       }),