修复空值检查问题

ruoyi-fastapi-backend/module_admin/controller/ragflow_controller.py

@@ -169,6 +169,15 @@ def stream_ragflow_response(result: Generator, chat_id: str, start_time: float)
             if isinstance(body, dict) and 'answer' in body:
                 current_answer = body['answer']
                 
+                # 安全检查：确保current_answer不为None且为字符串
+                if current_answer is None:
+                    logger.warning(f"[RAG_SERVER {chunk_time:.3f}] ⚠️ current_answer为None，跳过处理")
+                    continue
+                
+                if not isinstance(current_answer, str):
+                    logger.warning(f"[RAG_SERVER {chunk_time:.3f}] ⚠️ current_answer不是字符串，类型: {type(current_answer)}")
+                    current_answer = str(current_answer)
+                
                 # 计算增量内容
                 if current_answer.startswith(last_answer):
                     delta = current_answer[len(last_answer):]