fix: model answers가 있을 때만 DB에 쌓이도록 함

apps/answer/schemas.py

@@ -11,4 +11,3 @@ class UserAnswerSchema(Schema):
     id: int
     question: str
     model_answers: list[ModelAnswerSchema]
-

apps/chat/endpoints.py

@@ -104,8 +104,9 @@ def event_stream():
                     active_responses[model] = False
                     yield f"data: {json.dumps({'type': 'error', 'model': model, 'error': str(e)}, ensure_ascii=False)}\n\n"
 
-        answer = UserAnswer(question=message_data.message)
-        answer.save()
+        if text.keys():
+            answer = UserAnswer(question=message_data.message)
+            answer.save()
         model_answers = []
         for model_id in text.keys():
             model_answers.append(ModelAnswer(model_id=model_id, answer=text[model_id], user_answer=answer))