Refactor safety response handling in guardrails.mdx

Author: mcavdar

src/oss/langchain/guardrails.mdx

@@ -484,13 +484,7 @@ class SafetyGuardrailMiddleware(AgentMiddleware):
         result = self.safety_model.invoke([{"role": "user", "content": safety_prompt}])
 
         if "UNSAFE" in result.content:
-            return {
-                "messages": [{
-                    "role": "assistant",
-                    "content": "I cannot provide that response. Please rephrase your request."
-                }],
-                "jump_to": "end"
-            }
+            last_message.content = "I cannot provide that response. Please rephrase your request."
 
         return None