[O] org-irc.el get IRC link port error

[address@hidden]

Here is the steps to reproduce this issue:

Emacs version: 26.0.50 (from source code repo master branch)

Org-mode version: 9.0.8 (from source code repo master branch)

Here is the example link:

IRC: [[irc://irc.freenode.net/#nextcloud][#nextcloud]] on Freenode

I use Edebug to debug on function `org-irc-visit-erc`:

- [-] check out source code

  - [X] org-open-at-point(nil)

  - [X] org-irc-visit("//irc.freenode.net/#nextcloud")

  - [ ] org-irc-visit-erc((("irc.freenode.net") "#nextcloud"))

    - [ ] (port (or (string-to-number (cadr (pop link))) erc-default-port))

      - [ ] (string-to-number (cadr (pop link)))

        - [ ] (cadr (pop link)) -> (cadr ("irc.freenode.net")) -> nil

          #+BEGIN_SRC emacs-lisp

          (setq temp-link '(("irc.freenode.net") ("#clojure")))

          (pop temp-link)

          (cadr (pop temp-link))

          #+END_SRC

        - [ ] (string-to-number nil)

You can see what's wrong.

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