Avoid reqwest panic on invalid URIs

[mre]

Temporary workaround for #539 until the issue gets fixed upstream.

[lebensterben]

I still wonder why reqwest cannot accept URLs like https://web.archive.org/web/20131015212820/http://www.deviantart.com/

This can be opened in browser.

[mre]

If I change the test to your URL it works:

let client = ClientBuilder::builder().build().client().unwrap();
let res = client
    .check("https://web.archive.org/web/20131015212820/http://www.deviantart.com/")
    .await
    .unwrap();
assert!(res.status().is_success());

So it doesn't panic on that.
I will mention that in the original issue. (@dend fyi)

But the URL that I use in this PR (http://\") does panic.