fix .env loading

lib/src/services/deck_repository.dart

@@ -100,7 +100,15 @@ class DeckRepository {
   }
 
   Future<String?> loadApiKey() async {
-    final envApiKey = dotenv.env['WANIKANI_API_KEY'];
+    String? envApiKey;
+    try {
+      envApiKey = dotenv.env['WANIKANI_API_KEY'];
+    } catch (e) {
+      // dotenv is not initialized, so we can't get the key.
+      // This is expected in release builds.
+      envApiKey = null;
+    }
+
     if (envApiKey != null && envApiKey.isNotEmpty) {
       _apiKey = envApiKey;
       return _apiKey;
@@ -405,4 +413,4 @@ class DeckRepository {
     await saveVocabulary(items);
     return items;
   }
-}
+}

pubspec.yaml

@@ -34,5 +34,4 @@ flutter_icons:
 flutter:
   uses-material-design: true
   assets:
-    - assets/sfx/confirm.mp3
+    - assets/sfx/confirm.mp3
-    - .env