Hi,
Since the defect was critical and to avoid missing the 3.9 release, I cooked a fix (1) for the issue.
The latest offending code is found in an external library (2) and would require updating it.
I don't think it's wise doing it just before release since we won't have the time to make sure nothing breaks.
Your modules may also be affected. You can easily check that using the recipes I added to the issue (3).
Cheers,
(1)
https://github.com/Dolibarr/dolibarr/pull/4603(2) htdocs/includes/phpoffice/phpexcel/Classes/PHPExcel/Worksheet/AutoFilter/Column.php