bug: chatting with an assistant without files fails silently

[justinthelaw]

Environment

1. OS and Architecture: Ubuntu 22.04 AMD64
2. App or Package Name: leapfrogai-api
3. App or Package Version: main
4. Kubernetes Distribution: uds-k3d
5. Kubernetes Version: 1.28.8
6. Other: N/A

Steps to reproduce

1. Create an assistant without a file attached in the UI
2. Chat with the assistant

Expected result

• Chat message is returned from the run

Actual Result

• The run fails as the API router's request builder expects a file_ids to not be empty

Visual Proof (screenshots, videos, text, etc)

Traceback (most recent call last):                                                                                                                               
  File "/leapfrogai/.venv/lib/python3.11/site-packages/starlette/responses.py", line 257, in wrap                                                                
    await func()                                                                                                                                                 
  File "/leapfrogai/.venv/lib/python3.11/site-packages/starlette/responses.py", line 246, in stream_response                                                     
    async for chunk in self.body_iterator:                                                                                                                       
  File "/leapfrogai/.venv/lib/python3.11/site-packages/leapfrogai_api/routers/openai/requests/run_create_params_request_base.py", line 380, in stream_generate_message_for_thread                                                                                                                                                      
    chat_messages, file_ids = await self.create_chat_messages(                                                                                                   
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^                                                                                                   
  File "/leapfrogai/.venv/lib/python3.11/site-packages/leapfrogai_api/routers/openai/requests/run_create_params_request_base.py", line 286, in create_chat_messages                                                                                                                                                                    
    return chat_messages, list(file_ids)                                                                                                                         
                               ^^^^^^^^                                                                                                                          
UnboundLocalError: cannot access local variable 'file_ids' where it is not associated with a value 

Additional Context

N/A