fix(livetv): show guide without favorites

lib/models/livetv_channel.dart

@@ -31,6 +31,21 @@ String favoriteChannelKey(String source, String id) => '$source\u0000$id';
 String liveTvChannelScopeKey(LiveTvChannel channel) =>
     '${channel.serverId ?? ''}\u0000${channel.liveDvrKey ?? ''}\u0000${channel.key}';
 
+List<LiveTvChannel> filterLiveTvChannelsForFavorites({
+  required List<LiveTvChannel> channels,
+  required bool favoritesOnly,
+  required Iterable<FavoriteChannel> favorites,
+  required String Function(LiveTvChannel channel) sourceForChannel,
+}) {
+  if (!favoritesOnly || favorites.isEmpty) return channels;
+
+  final channelMap = {
+    for (final channel in channels) favoriteChannelKey(sourceForChannel(channel), channel.key): channel,
+  };
+
+  return [for (final favorite in favorites) ?channelMap[favorite.stableKey]];
+}
+
 @JsonSerializable(createToJson: false)
 class LiveTvChannel with MultiServerFields {
   @JsonKey(readValue: _readChannelKey)

lib/screens/livetv/live_tv_screen.dart

@@ -71,15 +71,12 @@ class _LiveTvScreenState extends State<LiveTvScreen>
   final Map<String, String> _favoriteStoreBySource = {};
   final Map<String, FavoriteChannelPersistenceMode> _favoriteModeByStore = {};
 
-  List<LiveTvChannel> get _filteredChannels {
-    if (!_showFavoritesOnly) return _channels;
-    if (_favoriteKeys.isEmpty) return const [];
-    final channelMap = {for (final c in _channels) _favoriteKeyForChannel(c): c};
-    return [
-      for (final fav in _favoriteChannels)
-        if (channelMap.containsKey(fav.stableKey)) channelMap[fav.stableKey]!,
-    ];
-  }
+  List<LiveTvChannel> get _filteredChannels => filterLiveTvChannelsForFavorites(
+    channels: _channels,
+    favoritesOnly: _showFavoritesOnly,
+    favorites: _favoriteChannels,
+    sourceForChannel: _sourceForChannel,
+  );
 
   String _liveServerScopeKey(LiveTvServerInfo serverInfo) => '${serverInfo.serverId}\u0000${serverInfo.dvrKey}';