Fix error when authorization header is nil

[koszta]

Fix error with Bandit when a client sends an empty Authorization header.

** (FunctionClauseError) no function clause matching in String.trim/1
    (elixir 1.16.2) lib/string.ex:1293: String.trim(nil)
    (guardian 2.3.2) lib/guardian/plug/verify_header.ex:167: Guardian.Plug.VerifyHeader.fetch_token_from_header/3
    (guardian 2.3.2) lib/guardian/plug/verify_header.ex:88: Guardian.Plug.VerifyHeader.call/2
    (api 0.0.1) ApiWeb.Router.guardian/2
    (api 0.0.1) lib/api_web/router.ex:1: ApiWeb.Router.__pipe_through0__/1
    (phoenix 1.7.12) lib/phoenix/router.ex:475: Phoenix.Router.__call__/5
    (api 0.0.1) deps/plug/lib/plug/error_handler.ex:80: ApiWeb.Router.call/2
    (api 0.0.1) lib/api_web/endpoint.ex:1: ApiWeb.Endpoint.plug_builder_call/2
Last message: {:continue, :start_stream}

[paulswartz]

This seems like a bug in Bandit? The type of req_headers says the value should always be a binary().

[yordis]

@koszta do you mind confirming that this is an expected behavior and it is not a bug in Bandit or something else?

[github-actions]

This pull request has been automatically marked as "stale:discard". If this pull request is still relevant, please leave any comment (for example, "bump"), and we'll keep it open. We are sorry that we haven't been able to prioritize reviewing it yet. Your contribution is very much appreciated!.

[koszta]

yes, it's clearly a bandit bug, closing it