Unreachable code reach on OpenAI Compatible

[netshade]

Recently I was using the OpenAI backend and trying to pass an image message to gpt-5 model. My code hit an unreachable panic at this line. My code roughly looked like the OpenAI vision example. I can try to create a repro, but was hoping for a bit of guidance first, in that I wonder if I'm hitting some odd code path by specifying a gpt-5 model or similar that would cause an "image" message not be sent to OpenAI ( at least, the example makes me think it's supposed to be able to receive image bytes as part of the message ).