Bug: 9.4 Regression in handling of empty #+TAGS: [9.4 (9.4-elpaplus @ /home/ionasal/.emacs.d/elpa/org-plus-contrib-20200914/)]

[Allen Li]

Previously, placing an empty #+TAGS: in a file would override
org-file-tags for the file.  In 9.4, an empty #+TAGS: is ignored and
org-file-tags is used.

The relevant code in org.el:

      (setq org-current-tag-alist
            (org--tag-add-to-alist
             org-tag-persistent-alist
             (let ((tags (mapconcat #'identity
                                    (cdr (assoc "TAGS" alist))
                                    "\n")))
               (if (org-string-nw-p tags) (org-tag-string-to-alist tags)
                 org-tag-alist))))

This regression is undesirable because I have a set of common
org-file-tags for most files, but one particular file where
automatically detecting the existing tags in the file works better (the
default behavior when org-current-tag-alist is empty).

Emacs  : GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.22, 
cairo version 1.17.3)
 of 2020-08-28
Package: Org mode version 9.4 (9.4-elpaplus @ 
/home/ionasal/.emacs.d/elpa/org-plus-contrib-20200914/)