Panic with `a` selector

[nilp0inter]

Hi!

I am getting this error consistently.

$ htmlq --version
htmlq 0.4.0
$ RUST_BACKTRACE=full htmlq a --base https://www.sede.fnmt.gob.es/descargas/certificados-raiz-de-la-fnmt -B --attribute href < <(curl -s --output - https://www.sede.fnmt.gob.es/descargas/certificados-raiz-de-la-fnmt)
thread 'main' panicked at src/link.rs:15:42:
called `Result::unwrap()` on an `Err` value: InvalidPort
stack backtrace:
   0:     0x56287552a365 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hee93a2ee0c2227c5
   1:     0x5628755660dc - core::fmt::write::h7222d6bd37096f9b
   2:     0x56287552a045 - std::io::Write::write_fmt::hf5bd345a4857fa1f
   3:     0x56287552a134 - std::sys_common::backtrace::print::h87f644093c44c474
   4:     0x562875538013 - std::panicking::default_hook::{{closure}}::h54f259bcb3c96d54
   5:     0x562875537d6a - std::panicking::default_hook::h4e7363e714c56f43
   6:     0x56287553849d - std::panicking::rust_panic_with_hook::h4be469481b88451f
   7:     0x56287552a9d2 - std::panicking::begin_panic_handler::{{closure}}::h12fd05c40e3f67ec
   8:     0x56287552a576 - std::sys_common::backtrace::__rust_end_short_backtrace::hda2ba2e5aeedda76
   9:     0x562875538194 - rust_begin_unwind
  10:     0x562875467cb5 - core::panicking::panic_fmt::h993794e49879741f
  11:     0x562875467bf3 - core::result::unwrap_failed::hb05442a284093f3a
  12:     0x5628754b127f - htmlq::link::rewrite_relative_urls::hb14e5d2a7485744f
  13:     0x5628754a280e - htmlq::main::he25b937698a12a70
  14:     0x5628754aaba3 - std::sys_common::backtrace::__rust_begin_short_backtrace::hf448e3e07a8968ae
  15:     0x5628754ae669 - std::rt::lang_start::{{closure}}::h9960a3e08a636b1b
  16:     0x562875538094 - std::panicking::try::h8ebc32e168e5ed61
  17:     0x5628755255ab - std::rt::lang_start_internal::h5dd16626185ad212
  18:     0x5628754a4645 - main
  19:     0x7fae0eec514e - __libc_start_call_main
  20:     0x7fae0eec5209 - __libc_start_main@@GLIBC_2.34
  21:     0x562875468145 - _start
  22:                0x0 - <unknown>

Cheers,
Roberto