fix: openai payload issue

backend/open_webui/apps/openai/main.py

@@ -411,7 +411,12 @@ async def generate_chat_completion(
     # Change max_completion_tokens to max_tokens (Backward compatible)
     if "api.openai.com" not in url and not payload["model"].lower().startswith("o1-"):
         if "max_completion_tokens" in payload:
-            payload["max_tokens"] = payload.pop("max_completion_tokens")
+            # Remove "max_completion_tokens" from the payload
+            payload["max_tokens"] = payload["max_completion_tokens"]
+            del payload["max_completion_tokens"]
+    else:
+        if "max_tokens" in payload and "max_completion_tokens" in payload:
+            del payload["max_tokens"]
 
     # Convert the modified body back to JSON
     payload = json.dumps(payload)