bug#48182: 28.0.50; Assertion fails when completing at beginning of org #+TITLE

bug#48182: 28.0.50; Assertion fails when completing at beginning of org #+TITLE

[Steven Bagley]

1. emacs -Q
2. (setq tab-always-indent 'complete)
3. create a new empty buffer in org-mode
4. enter the following text:
#+TITLE: testing
5. put the cursor at the first buffer position.
6. Hit TAB. The following message shows:

cl--assertion-failed: Assertion failed: (<= start (point)), #<marker at 
10 in test.org>, 1



In GNU Emacs 28.0.50 (build 1, x86_64-apple-darwin19.6.0, NS 
appkit-1894.60 Version 10.15.7 (Build 19H1030))
  of 2021-05-01 built on cadr.local
Repository revision: f1adb6b77a948e4f2f3223940edb15e56c30466d
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1894
System Description:  Mac OS X 10.15.7

Configured features:
ACL DBUS GNUTLS JSON LCMS2 LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER PNG
THREADS TOOLKIT_SCROLL_BARS ZLIB

Important settings:
   value of $LANG: en_US.UTF-8
   locale-coding-system: utf-8-unix

Major mode: Messages

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   buffer-read-only: t
   line-number-mode: t
   transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug sendmail org-element avl-tree generator
ol-eww eww xdg url-queue thingatpt mm-url ol-rmail ol-mhe ol-irc ol-info
ol-gnus nnselect gnus-search eieio-opt cl-extra help-mode speedbar
ezimage dframe gnus-art mm-uu mml2015 mm-view mml-smime smime dig
gnus-sum shr kinsoku svg dom browse-url url url-proxy url-privacy
url-expand url-methods url-history url-cookie url-domsuf url-util
url-parse url-vars mailcap gnus-group gnus-undo gnus-start gnus-dbus
dbus xml gnus-cloud nnimap nnmail mail-source utf7 netrc nnoo parse-time
gnus-spec gnus-int gnus-range message rmc puny rfc822 mml mml-sec epa
derived epg epg-config mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader gnus-win gnus nnheader gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map rfc2047 rfc2045 ietf-drums
text-property-search seq byte-opt gv bytecomp byte-compile cconv
mail-utils mm-util mail-prsvr wid-edit ol-docview doc-view jka-compr
image-mode exif dired dired-loaddefs ol-bibtex bibtex iso8601 ol-bbdb
ol-w3m org ob ob-tangle ob-ref ob-lob ob-table ob-exp org-macro
org-footnote org-src ob-comint org-pcomplete pcomplete comint ansi-color
ring org-list org-faces org-entities time-date subr-x noutline outline
easy-mmode org-version ob-emacs-lisp ob-core ob-eval org-table ol
org-keys org-compat advice org-macs org-loaddefs format-spec find-func
cal-menu calendar cal-loaddefs cl-loaddefs cl-lib iso-transl tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
term/ns-win ns-win ucs-normalize mule-util term/common-win tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads dbusbind
kqueue cocoa ns lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 170636 11712)
  (symbols 48 19054 1)
  (strings 32 65879 2383)
  (string-bytes 1 2187141)
  (vectors 16 34901)
  (vector-slots 8 383947 21475)
  (floats 8 240 81)
  (intervals 56 266 0)
  (buffers 992 12))