[BUG] Face of Org block ending line (org-block-end-line) propagates to next line. [9.6.6 (release_9.6.6 @ /usr/share/emacs/29.1/lisp/org/)]

[Kostas Papadakis <papadakis.k@yandex.com>]

Summary: The face org-block-end-line is propagating to the next line
causing graphic anomalies when it's customized with anything like
background, underline, overline etc.

How to reproduce:
Start a new Emacs instance with the command "emacs -Q".
Issue find-file and create a new org file buffer and insert
just the following two lines of text (i.e. an empty source block):
#+begin_src
#+end_src

Place the cursor at the end of the 2nd line (which should also be the
last character in the buffer), i.e like here:
#+end_src[_]

And issue the describe-face command. You will notice it's using the
default face. Now run the open-line command (C-o by default) in order to
insert a new line below, and rerun the describe-face from the same
cursor position. You will notice now that we get the org-block-end-line
face (which is in accordance to how the face org-block-begin-line is
working). So far so good. Now from this same position press the Enter
key. This should move the cursor to the start of the third line of our
buffer. Now issue the describe-face command again. You will notice that
the org-block-end-line face still applies on the new line (while the
right face here would be the default). If we start writing something on
the third line, the org-block-end-line face goes away and default face
comes in, "fixing" the issue.

Now this is becoming really annoying when you have a theme that you
customize org-block-end-line with :extend t and anything like
:background, :box, :underline, :overline. The face would propagate on
the next line, and create ugly artifacts on the screen.

------------------------------------------------------------------------

Emacs  : GNU Emacs 29.1 (build 2, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0, Xaw3d scroll bars)
  of 2023-08-30, modified by Debian
Package: Org mode version 9.6.6 (release_9.6.6 @ /usr/share/emacs/29.1/lisp/org/)

current state:
==============
(setq
  org-link-elisp-confirm-function 'yes-or-no-p
  org-bibtex-headline-format-function #[257 "\300\x01\236A\207" [:title] 3 "\n\n(fn ENTRY)"]
  org-persist-after-read-hook '(org-element--cache-persist-after-read)
  org-export-before-parsing-hook '(org-attach-expand-links)
  org-cycle-tab-first-hook '(org-babel-hide-result-toggle-maybe
			    org-babel-header-arg-expand)
  org-archive-hook '(org-attach-archive-delete-maybe)
  org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-show-empty-lines
		  org-cycle-optimize-window-after-visibility-change
		  org-cycle-display-inline-images)
  org-persist-before-read-hook '(org-element--cache-persist-before-read)
  org-mode-hook '(#[0 "\300\301\302\303\304$\207"
		   [add-hook change-major-mode-hook org-fold-show-all append
		    local]
		   5]
		 #[0 "\300\301\302\303\304$\207"
		   [add-hook change-major-mode-hook org-babel-show-result-all
		    append local]
		   5]
		 org-babel-result-hide-spec org-babel-hide-all-hashes)
  org-confirm-shell-link-function 'yes-or-no-p
  outline-isearch-open-invisible-function 'outline-isearch-open-invisible
  org-agenda-before-write-hook '(org-agenda-add-entry-text)
  org-src-mode-hook '(org-src-babel-configure-edit-buffer
		     org-src-mode-configure-edit-buffer)
  org-confirm-elisp-link-function 'yes-or-no-p
  org-speed-command-hook '(org-speed-command-activate
			  org-babel-speed-command-activate)
  org-persist-directory "/tmp/org-persist-NEwgDE"
  org-fold-core-isearch-open-function 'org-fold--isearch-reveal
  org-persist-before-write-hook '(org-element--cache-persist-before-write)
  org-tab-first-hook '(org-babel-hide-result-toggle-maybe
		      org-babel-header-arg-expand)
  org-link-shell-confirm-function 'yes-or-no-p
  org-babel-pre-tangle-hook '(save-buffer)
  org-agenda-loop-over-headlines-in-active-region nil
  org-occur-hook '(org-first-headline-recenter)
  org-metadown-hook '(org-babel-pop-to-session-maybe)
  org-link-parameters '(("attachment" :follow org-attach-follow :complete
			org-attach-complete-link)
		       ("id" :follow org-id-open)
		       ("eww" :follow org-eww-open :store org-eww-store-link)
		       ("rmail" :follow org-rmail-open :store
			org-rmail-store-link)
		       ("mhe" :follow org-mhe-open :store org-mhe-store-link)
		       ("irc" :follow org-irc-visit :store org-irc-store-link
			:export org-irc-export)
		       ("info" :follow org-info-open :export org-info-export
			:store org-info-store-link :insert-description
			org-info-description-as-command)
		       ("gnus" :follow org-gnus-open :store
			org-gnus-store-link)
		       ("docview" :follow org-docview-open :export
			org-docview-export :store org-docview-store-link)
		       ("bibtex" :follow org-bibtex-open :store
			org-bibtex-store-link)
		       ("bbdb" :follow org-bbdb-open :export org-bbdb-export
			:complete org-bbdb-complete-link :store
			org-bbdb-store-link)
		       ("w3m" :store org-w3m-store-link)
		       ("doi" :follow org-link-doi-open :export
			org-link-doi-export)
		       ("file+sys") ("file+emacs")
		       ("shell" :follow org-link--open-shell)
		       ("news" :follow
			#[514 "\301\300\302\x04Q\x02\"\207"
			  ["news" browse-url ":"] 6 "\n\n(fn URL ARG)"]
			)
		       ("mailto" :follow
			#[514 "\301\300\302\x04Q\x02\"\207"
			  ["mailto" browse-url ":"] 6 "\n\n(fn URL ARG)"]
			)
		       ("https" :follow
			#[514 "\301\300\302\x04Q\x02\"\207"
			  ["https" browse-url ":"] 6 "\n\n(fn URL ARG)"]
			)
		       ("http" :follow
			#[514 "\301\300\302\x04Q\x02\"\207"
			  ["http" browse-url ":"] 6 "\n\n(fn URL ARG)"]
			)
		       ("ftp" :follow
			#[514 "\301\300\302\x04Q\x02\"\207" ["ftp" browse-url ":"]
			  6 "\n\n(fn URL ARG)"]
			)
		       ("help" :follow org-link--open-help :store
			org-link--store-help)
		       ("file" :complete org-link-complete-file)
		       ("elisp" :follow org-link--open-elisp))
  org-metaup-hook '(org-babel-load-in-session-maybe)
  )