panic when empty env https_proxy

[JasonHonor]

ureq_impl.rs:24

Agent::new_with_defaults().into()

cause panic while starting when there had an empty "https_proxy" env on manjaro linux with "ureq-3.0.3/src/proxy.rs:87:44"

called `Result::unwrap()` on an `Err` value: InvalidUri(Empty)

[jaytaph]

@JasonHonor Thanks for the bug report. It seems that ureq by default tries to detect if a proxy is needed by checking the environment settings (proxy::try_from_env()), however, it assumes that the string passed (by HTTPS_PROXY or any other proyxy env settings) is a correct URI.. It doesn't check if this URI is invalid:

I've added a PR to their repo with a fix. Hopefully they will merge it:

algesten/ureq#990