[BUG] Extra trailing backgrounds leftover after unfolding org headlines [9.7 (9.7-??-902dacb @ /home/st/.config/emacs/.local/straight/build-30.0.50/org/)]

[StrawberryTea <look@strawberrytea.xyz>]

Hello Org mode developers,

I've noticed that when I unfold an org headline, a trailing background
is sometimes left behind at the end of the body text.

Here is a minimal example to reproduce the issue from emacs -Q:

;; Bootstrap straight
(defvar bootstrap-version)

(let ((bootstrap-file
       (expand-file-name "straight/repos/straight.el/bootstrap.el" user-emacs-directory))
      (bootstrap-version 5))
  (unless (file-exists-p bootstrap-file)
    (with-current-buffer
        (url-retrieve-synchronously "https://raw.githubusercontent.com/raxod502/straight.el/develop/install.el"
                                    'silent 'inhibit-cookies)
      (goto-char (point-max))
      (eval-print-last-sexp)))
  (load bootstrap-file nil 'nomessage))

(straight-use-package 'org)

(require 'org)
(load-theme 'leuven t)

(dolist (face '(org-level-1 org-level-2 org-level-3 org-level-4 org-level-5
                org-level-6 org-level-7 org-level-8))
  (set-face-attribute face nil :extend t))

(setq org-fontify-whole-heading-line t)
(scratch-buffer)
(org-mode)
(insert "* Headline 1\n Hello
* Headline 1\nHello\n")

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.
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Emacs  : GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.18.0)
 of 2024-03-02
Package: Org mode version 9.7 (9.7-??-902dacb @ /home/st/.config/emacs/.local/straight/build-30.0.50/org/)