fix by review

optuna_dashboard/_app.py

@@ -312,7 +312,7 @@ def create_app(
 
     @app.put("/api/studies/<study_id:int>/preference_feedback_component_type")
     @json_api_view
-    def put_component(study_id: int) -> dict[str, Any]:
+    def put_preference_feedback_component_type(study_id: int) -> dict[str, Any]:
         try:
             component_type = request.json.get("type", "")
             artifact_key = request.json.get("artifact_key", None)
@@ -329,6 +329,8 @@ def create_app(
             component_type=component_type,
             artifact_key=artifact_key,
         )
+        response.status = 204
+        return {}
 
     @app.delete("/api/studies/<study_id:int>/preference/<history_id>")
     @json_api_view

optuna_dashboard/_serializer.py

@@ -168,7 +168,6 @@ def serialize_study_detail(
         serialized["feedback_component_type"] = system_attrs.get(
             _SYSTEM_ATTR_FEEDBACK_COMPONENT, {}
         )
-    if serialized["is_preferential"]:
         serialized["preference_history"] = serialize_preference_history(system_attrs)
         serialized["preferences"] = get_preferences(system_attrs)
     serialized["plotly_graph_objects"] = [