fix tests

packages/stream_chat/lib/src/core/models/own_user.g.dart

@@ -39,6 +39,6 @@ OwnUser _$OwnUserFromJson(Map<String, dynamic> json) {
     teams:
         (json['teams'] as List<dynamic>?)?.map((e) => e as String).toList() ??
             [],
-    language: json['language'] as String,
+    language: json['language'] as String?,
   );
 }

packages/stream_chat/test/fixtures/user.json

@@ -1,5 +1,6 @@
 {
   "id": "bbb19d9a-ee50-45bc-84e5-0584e79d0c9e",
   "role": "test-role",
-  "name": "John"
+  "name": "John",
+  "language": "en"
 }