fix: guard against empty choices and message=None in load test proxy

cookbook/litellm_router/load_test_proxy.py

@@ -97,6 +97,8 @@ def make_openai_completion(question):
         end_time = time.time()
 
         # Log the request details
+        if not response.choices or response.choices[0].message is None:
+            raise ValueError("LLM returned empty or filtered response")
         with open("request_log.txt", "a") as log_file:
             log_file.write(
                 f"Question: {question[:100]}\nResponse ID:{response.id} Content:{response.choices[0].message.content[:10]}\nTime: {end_time - start_time:.2f} seconds\n\n"