Make the reponse mapping more robust by checking for an empty (or
missing) `choices` list and substitute a list with an empty dictionary.
Use `.get` to access the `message` or `delta` object again returning an
empty dictionary if they are not found.
When using `hermes3-405b` on lambda cloud's inference (based on
openrouter) a final response was returned with an empty list for
choices causing a traceback on completion.
Debug log:
```
[2024-12-11 19:49:11.925592] [engine-chat] response: {'id': 'chatcmpl-140a7a938d2149c8a750f47af6a11be1', 'object': 'chat.completion.chunk', 'created': 1733946550, 'model': 'hermes3-405b', 'choices': [{'index': 0, 'delta': {'content': ' today'}, 'finish_reason': None, 'content_filter_results': {'hate': {'filtered': False}, 'self_harm': {'filtered': False}, 'sexual': {'filtered': False}, 'violence': {'filtered': False}, 'jailbreak': {'filtered': False, 'detected': False}, 'profanity': {'filtered': False, 'detected': False}}}], 'system_fingerprint': '', 'usage': {'prompt_tokens': 40, 'completion_tokens': 18, 'total_tokens': 58, 'prompt_tokens_details': None, 'completion_tokens_details': None}}
[2024-12-11 19:49:11.975457] [engine-chat] response: {'id': 'chatcmpl-140a7a938d2149c8a750f47af6a11be1', 'object': 'chat.completion.chunk', 'created': 1733946550, 'model': 'hermes3-405b', 'choices': [{'index': 0, 'delta': {'content': '?'}, 'finish_reason': None, 'content_filter_results': {'hate': {'filtered': False}, 'self_harm': {'filtered': False}, 'sexual': {'filtered': False}, 'violence': {'filtered': False}, 'jailbreak': {'filtered': False, 'detected': False}, 'profanity': {'filtered': False, 'detected': False}}}], 'system_fingerprint': '', 'usage': {'prompt_tokens': 40, 'completion_tokens': 19, 'total_tokens': 59, 'prompt_tokens_details': None, 'completion_tokens_details': None}}
[2024-12-11 19:49:12.008987] [engine-chat] response: {'id': 'chatcmpl-140a7a938d2149c8a750f47af6a11be1', 'object': 'chat.completion.chunk', 'created': 1733946550, 'model': 'hermes3-405b', 'choices': [{'index': 0, 'delta': {}, 'finish_reason': 'stop', 'content_filter_results': {'hate': {'filtered': False}, 'self_harm': {'filtered': False}, 'sexual': {'filtered': False}, 'violence': {'filtered': False}, 'jailbreak': {'filtered': False, 'detected': False}, 'profanity': {'filtered': False, 'detected': False}}}], 'system_fingerprint': '', 'usage': {'prompt_tokens': 40, 'completion_tokens': 20, 'total_tokens': 60, 'prompt_tokens_details': None, 'completion_tokens_details': None}}
[2024-12-11 19:49:12.009400] [engine-chat] response: {'id': 'chatcmpl-140a7a938d2149c8a750f47af6a11be1', 'object': 'chat.completion.chunk', 'created': 1733946550, 'model': 'hermes3-405b', 'choices': [], 'system_fingerprint': '', 'usage': {'prompt_tokens': 40, 'completion_tokens': 19, 'total_tokens': 59, 'prompt_tokens_details': None, 'completion_tokens_details': None}}
```