bugfix(Azure): fix index out of range error due to Azure Openai reponses an empty chunk at first

[zfanswer]

Description

Azure Openai reponse may have an empty chunk at the first streming response, i.e. the "choices" key have an empty list.
This will cause the error from reponse json parser.

You can see the "choices": [] at the first response.

Solution

Do a empty/None check before parse the response json.

[fangyinc]

LGTM.

[fangyinc]

Hi, @zfanswer, thank you for your PR. Please address the code formatting issues. You can install black with pip install black, and then run black . in the project directory to format the Python code.

[zfanswer]

Hi, @zfanswer, thank you for your PR. Please address the code formatting issues. You can install black with pip install black, and then run black . in the project directory to format the Python code.

didn't get the notice,...
black . is done.

[fangyinc]

LGTM.