A strange auto typesetting problem when using auctex.

[Hongyi Zhao]

On Ubuntu 20.04, I use the latest git master Emacs version compiled by
myself. I install and load auctex's git master version with the
following bootstrap code in `~/.emacs.d/init.el':

;;Bootstrap auctex via straight
(straight-use-package
 `( auctex :type git :host nil :repo
"https://git.savannah.gnu.org/git/auctex.git";
    :pre-build ,(pcase system-type
                (`berkeley-unix '("gmake"))
                (_ '(
                    ;("bash" "-c" "cd ~/.emacs.d/straight/repos/auctex")
                    ("./autogen.sh")
                    ("./configure")
                    ("make")
                    ("sudo" "make" "install"))))))

(load "auctex.el" nil t t)
(load "preview-latex.el" nil t t)
;;; auctex config ends here

Then I try to test auctex with the following LaTeX sample file:

%% LaTeX sample file
\documentclass{paper}
\usepackage{hyperref}
\begin{document}
See
\href{http://www.fulviofrisone.com/attachments/article/480/Ballentine%20L.%20Quantum%20mechanics%20-%20a%20modern%20development%20(1998)(T)(673s).pdf}{page
98}
\end{document}
%% LaTeX sample file ends here

When I put the point after the `{page 98}' and hit RET, the LaTeX file
will be automatically completed into the following:

%% LaTeX sample file
\documentclass{paper}
\usepackage{hyperref}
\begin{document}
See
\href{http://www.fulviofrisone.com/attachments/article/480/Ballentine%20L.%20Quantum%20mechanics%20-%20a%20modern%20development%20(1998)(T)(673s).pdf}{page
  % 98}

\end{document}
%% LaTeX sample file ends here

As you can see, the auto-completed typesetting result is wrong due to
the leading `%' before ` 98}'.

Any hints for this problem?

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
NO. 552 North Gangtie Road, Xingtai, China