[BUG] Bug: Footnotes break iCalendar export [9.4.6 (9.4.6-g069bcb @ /home/msi/.emacs.d/straight/build/org/)]

[msi]

Remember to cover the basics, that is, what you expected to happen and
what in fact did happen.  You don't know how to make a good report?  See

     https://orgmode.org/manual/Feedback.html#Feedback

Your bug report will be posted to the Org mailing list.
------------------------------------------------------------------------

Hello,


When I make the function "org-icalendar-combine-agenda-files", all it's
ok. But, when I add a footnote, I have this in my .ics file :

BEGIN:VEVENT.
DTSTAMP:20211116T101642Z.
UID:SC-6a6cf716-f056-4116-a419-5f0e96b14fd9.
DTSTART;VALUE=DATE:20220516.
DTEND;VALUE=DATE:20220517.
SUMMARY:S: Prehistoric Kingdom.
CATEGORIES:5References(liensTextes),TODO.
END:VEVENT



Footnotes
─────────

a footnote

another
END:VCALENDAR

I think that is the same bug of this thread :
https://lists.gnu.org/archive/html/emacs-orgmode/2013-04/msg01478.html

So I add too this line:
(footnote-definition . ignore)
in ox-ascii.el, but it doesn't works.

Thank you in advance




Emacs  : GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, 
cairo version 1.16.0)
 of 2020-09-19
Package: Org mode version 9.4.6 (9.4.6-g069bcb @ 
/home/msi/.emacs.d/straight/build/org/)