init audio_file variable

[jcaiqueoliveira]

After

curl -X POST -H "Content-type: application/json" -d "{\"question\" : \"I have a flask api that needs to validate the schema of a POST body, how do I do that?\"}" http://127.0.0.1:5000/ask

Received the following error
UnboundLocalError: local variable 'audio_file' referenced before assignment

Setting audio_file = None fixes it