GNU Emacs 28.0.50 smex/smex.el: Warning: (lambda nil \.\.\.) quoted with ' rather than with #'

Steps to reproduce

$ emacs -Q

Eval code

  (let ((smex-location (expand-file-name "~/.emacs.d/smex")))
    (unless (file-directory-p smex-location)
      (shell-command
       (format
        "git clone https://github.com/nonsequitur/smex.git %s"
        smex-location)))
    (add-to-list 'load-path smex-location))
  (require 'smex)
  (smex-initialize)

Error

smex/smex.el: Warning: (lambda nil \.\.\.) quoted with ' rather than with #'