Otherwise valid code can panic on workspace exhaustion:

    std.ip(req.http.X-Real-IP, std.ip(req.http.X-Client-IP, client.ip))

If the nested std.ip() call runs out of workspace, it will return a null
ip instead of the fallback, and since the outer std.ip() call is getting
a fallback argument, it will panic upon checking the suckaddr sanity.

Refs a3b26d0b