[Feature]: Return cacheable profile picture as fallback

[bt90]

Feature detail

Currently, if an account does not have a profile picture associated with it, the API responds with an (at least for Firefox) uncacheable 404:

Maybe we could use HTTP 204 instead?

https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/204

A 204 response is cacheable by default

Platform

Web

[uhthomas]

Given the response body will be zero bytes either way, I don't see the value of using 204? The browser would have to revalidate anyway and would so the behaviour would be no different.