Fix variable shadowing and add login check

- Rename loop variable 'message' to 'chunk' to avoid shadowing the function parameter
- Add None check for hf_token when user is not logged in

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app.py

@@ -14,6 +14,10 @@ def respond(
     """
     For more information on `huggingface_hub` Inference API support, please check the docs: https://huggingface.co/docs/huggingface_hub/v0.22.2/en/guides/inference
     """
+    if hf_token is None:
+        yield "⚠️ Silakan login dulu dengan tombol Login di sidebar."
+        return
+
     client = InferenceClient(token=hf_token.token, model="openai/gpt-oss-20b")
 
     messages = [{"role": "system", "content": system_message}]
@@ -24,14 +28,14 @@ def respond(
 
     response = ""
 
-    for message in client.chat_completion(
+    for chunk in client.chat_completion(
         messages,
         max_tokens=max_tokens,
         stream=True,
         temperature=temperature,
         top_p=top_p,
     ):
-        choices = message.choices
+        choices = chunk.choices
         token = ""
         if len(choices) and choices[0].delta.content:
             token = choices[0].delta.content