Warn against Falsy credentials (#8683)
* fix(auth): Disallow Falsy credentials
Allowing Falsy auth credentials will cause problems later, for example in `hmac.compare_digest(input_password.encode(), correct_password.encode())` as NoneType has no `encode` method. Moreover, allowing empty passwords would make no sense from a security point of view.
* fix(auth): Produce warning instead of raising an error
* add changeset
* add changeset
---------
Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>
