fix: guard unsafe .first/.last calls to prevent StateError

lib/providers/companion_remote_provider.dart

@@ -226,6 +226,10 @@ class CompanionRemoteProvider with ChangeNotifier {
   }
 
   Future<void> joinSessionMulti(String sessionId, String pin, List<String> hostAddresses) async {
+    if (hostAddresses.isEmpty) {
+      throw ArgumentError('hostAddresses must not be empty');
+    }
+
     await leaveSession();
 
     _lastSessionId = sessionId;

lib/providers/offline_watch_provider.dart

@@ -145,7 +145,7 @@ class OfflineWatchProvider extends ChangeNotifier {
     }
 
     // All episodes watched - return first episode for replay
-    return episodes.first;
+    return episodes.firstOrNull;
   }
 
   /// Find the next unwatched downloaded episode synchronously.
@@ -164,7 +164,7 @@ class OfflineWatchProvider extends ChangeNotifier {
     }
 
     // All episodes watched - return first episode for replay
-    return episodes.first;
+    return episodes.firstOrNull;
   }
 
   /// Emit a watch state change event for immediate UI update.

lib/providers/playback_state_provider.dart

@@ -210,7 +210,7 @@ class PlaybackStateProvider with ChangeNotifier {
     }
 
     // Need to load next window
-    if (_client != null && _playQueueId != null) {
+    if (_client != null && _playQueueId != null && _loadedItems.isNotEmpty) {
       // Load next window centered on the item after current
       final nextItemID = _loadedItems.last.playQueueItemID;
       if (nextItemID != null) {
@@ -248,7 +248,7 @@ class PlaybackStateProvider with ChangeNotifier {
     }
 
     // Need to load previous window
-    if (_client != null && _playQueueId != null) {
+    if (_client != null && _playQueueId != null && _loadedItems.isNotEmpty) {
       final prevItemID = _loadedItems.first.playQueueItemID;
       if (prevItemID != null && prevItemID > 0) {
         final loaded = await _ensureItemsLoaded(prevItemID - 1);

lib/screens/base_media_list_detail_screen.dart

@@ -59,10 +59,10 @@ abstract class BaseMediaListDetailScreen<T extends StatefulWidget> extends State
     // If serverId is null, fall back to first available server
     if (serverId == null) {
       final multiServerProvider = Provider.of<MultiServerProvider>(context, listen: false);
-      if (!multiServerProvider.hasConnectedServers) {
+      serverId = multiServerProvider.onlineServerIds.firstOrNull;
+      if (serverId == null) {
         throw Exception(t.errors.noClientAvailable);
       }
-      serverId = multiServerProvider.onlineServerIds.first;
     }
 
     return context.getClientForServer(serverId);

lib/screens/discover_screen.dart

@@ -63,10 +63,11 @@ class _DiscoverScreenState extends State<DiscoverScreen>
   @override
   PlexClient get client {
     final multiServerProvider = Provider.of<MultiServerProvider>(context, listen: false);
-    if (!multiServerProvider.hasConnectedServers) {
+    final serverId = multiServerProvider.onlineServerIds.firstOrNull;
+    if (serverId == null) {
       throw Exception('No servers available');
     }
-    return context.getClientForServer(multiServerProvider.onlineServerIds.first);
+    return context.getClientForServer(serverId);
   }
 
   List<PlexMetadata> _onDeck = [];
@@ -140,10 +141,11 @@ class _DiscoverScreenState extends State<DiscoverScreen>
     final serverId = item?.serverId;
     if (serverId == null) {
       final multiServerProvider = Provider.of<MultiServerProvider>(context, listen: false);
-      if (!multiServerProvider.hasConnectedServers) {
+      final fallbackId = multiServerProvider.onlineServerIds.firstOrNull;
+      if (fallbackId == null) {
         throw Exception('No servers available');
       }
-      return context.getClientForServer(multiServerProvider.onlineServerIds.first);
+      return context.getClientForServer(fallbackId);
     }
     return context.getClientForServer(serverId);
   }

lib/screens/libraries/libraries_screen.dart

@@ -79,10 +79,11 @@ class _LibrariesScreenState extends State<LibrariesScreen>
   @override
   PlexClient get client {
     final multiServerProvider = Provider.of<MultiServerProvider>(context, listen: false);
-    if (!multiServerProvider.hasConnectedServers) {
+    final serverId = multiServerProvider.onlineServerIds.firstOrNull;
+    if (serverId == null) {
       throw Exception(t.errors.noClientAvailable);
     }
-    return context.getClientForServer(multiServerProvider.onlineServerIds.first);
+    return context.getClientForServer(serverId);
   }
 
   // GlobalKeys for tabs to enable refresh

lib/utils/provider_extensions.dart

@@ -50,10 +50,11 @@ extension ProviderExtensions on BuildContext {
     // If library doesn't have a serverId, fall back to first available server
     if (library.serverId == null) {
       final multiServerProvider = Provider.of<MultiServerProvider>(this, listen: false);
-      if (!multiServerProvider.hasConnectedServers) {
+      final serverId = multiServerProvider.onlineServerIds.firstOrNull;
+      if (serverId == null) {
         throw Exception(t.errors.noClientAvailable);
       }
-      return getClientForServer(multiServerProvider.onlineServerIds.first);
+      return getClientForServer(serverId);
     }
     return getClientForServer(library.serverId!);
   }
@@ -80,10 +81,11 @@ extension ProviderExtensions on BuildContext {
   /// Throws an exception if no servers are available
   PlexClient getFirstAvailableClient() {
     final multiServerProvider = Provider.of<MultiServerProvider>(this, listen: false);
-    if (!multiServerProvider.hasConnectedServers) {
+    final serverId = multiServerProvider.onlineServerIds.firstOrNull;
+    if (serverId == null) {
       throw Exception(t.errors.noClientAvailable);
     }
-    return getClientForServer(multiServerProvider.onlineServerIds.first);
+    return getClientForServer(serverId);
   }
 
   /// Get client for a serverId with fallback to first available server