remove empty stream response

src/llmtuner/api/chat.py

@@ -156,6 +156,7 @@ async def create_stream_chat_completion_response(
         top_p=request.top_p,
         max_new_tokens=request.max_tokens,
     ):
+        if len(new_token) != 0:
             yield _create_stream_chat_completion_chunk(
                 completion_id=completion_id, model=request.model, delta=ChatCompletionMessage(content=new_token)
             )