bug#70824: 29.3; Run time error in `dabbrev-completion'

[Matt Armstrong via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

I'm in a state where `dabbrev--last-buffer' is set to #<killed buffer>,
which confuses the `dabbrev-completion' command as shown by the 
backtrace below.

If I find a way to reproduce I will follow up with that.

I suspect that dabbrev.el should use `(buffer-live-p
dabbrev--last-buffer)' instead of checking for non-nil.

First, the value of dabbrev--last-buffer:

     dabbrev--last-buffer is a variable defined in ‘dabbrev.el’.
     Its value is #<killed buffer>
     Not documented as a variable.

Second, what happens when I run `dabbrev-completion':

Debugger entered--Lisp error: (error "Selecting deleted buffer")
   set-buffer(#<killed buffer>)
   (progn (set-buffer dabbrev--last-buffer))
   (if dabbrev--last-buffer (progn (set-buffer dabbrev--last-buffer)))
   (save-excursion (if dabbrev--last-buffer (progn (set-buffer 
dabbrev--last-buffer))) (or (and (not dabbrev-search-these-buffers-only) 
(>= direction 0) (setq dabbrev--last-direction (min 1 direction)) 
(dabbrev--try-find abbrev t (max 1 direction) ignore-case)) (and (or 
(not dabbrev-search-these-buffers-only) dabbrev--last-buffer) (<= 
direction 0) (setq dabbrev--last-direction -1) (dabbrev--try-find abbrev 
nil (max 1 (- direction)) ignore-case)) (progn (setq 
dabbrev--last-direction -1) (if dabbrev--last-buffer nil (if 
dabbrev--friend-buffer-list nil (setq dabbrev--friend-buffer-list 
(dabbrev--make-friend-buffer-list)) (setq dabbrev--progress-reporter 
(make-progress-reporter "Scanning for dabbrevs..." (- ...) 0 0 1 1.5)))) 
(let ((file-name (buffer-file-name)) file-name-buffer) (unwind-protect 
(progn (if file-name (progn ... ... ...)) (let (expansion) (while ... 
... ... ... ... ...) (progress-reporter-done dabbrev--progress-reporter) 
expansion)) (if (buffer-live-p file-name-buffer) (progn (kill-buffer 
file-name-buffer))) (setq dabbrev--friend-buffer-list (seq-filter 
#'buffer-live-p dabbrev--friend-buffer-list)))))))
   dabbrev--find-expansion("p" -1 t)
   dabbrev--find-all-expansions("p" t)
   #f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>)(#("p" 0 
1 (fontified t)) nil (boundaries . ""))
   completion-boundaries(#("p" 0 1 (fontified t)) #f(compiled-function 
(s p a) #<bytecode -0x1773fde4def7ae30>) nil "")
   completion-basic-try-completion(#("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1)
   #f(compiled-function (style) #<bytecode -0x1bb324416e7d7fbf>)(basic)
   completion--some(#f(compiled-function (style) #<bytecode 
-0x1bb324416e7d7fbf>) (basic partial-completion emacs22))
   completion--nth-completion(1 #("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1 
(metadata (cycle-sort-function . identity) (category . dabbrev)))
   completion-try-completion(#("p" 0 1 (fontified t)) 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil 1 
(metadata (cycle-sort-function . identity) (category . dabbrev)))
   completion--do-completion(#<marker at 531 in persist.rs> 532)
   completion--in-region-1(#<marker at 531 in persist.rs> 532)
   #f(compiled-function (start end collection predicate) #<bytecode 
-0x16fb47f8fb6a4d3d>)(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   apply(#f(compiled-function (start end collection predicate) 
#<bytecode -0x16fb47f8fb6a4d3d>) (#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil))
   #f(compiled-function (funs global args) #<bytecode 
-0x73c1f01704730a2>)(nil nil (#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil))
   completion--in-region(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   completion-in-region(#<marker at 531 in persist.rs> 532 
#f(compiled-function (s p a) #<bytecode -0x1773fde4def7ae30>) nil)
   completion-at-point()
   dabbrev-completion(nil)
   funcall-interactively(dabbrev-completion nil)
   command-execute(dabbrev-completion)




In GNU Emacs 29.3 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.41,
cairo version 1.18.0)
System Description: Debian GNU/Linux 12 (bookworm)

Configured using:
  'configure
  --prefix=/nix/store/m88zm8z7qrby6zlnq32z35nmn89jdzkl-emacs-pgtk-29.3
  --disable-build-details --with-modules --with-pgtk
  --with-compress-install --with-toolkit-scroll-bars
  --with-native-compilation --without-imagemagick --without-small-ja-dic
  --with-tree-sitter --without-xinput2 --with-xwidgets --with-dbus
  --with-selinux'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON
LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER
PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS
TREE_SITTER WEBP XIM XWIDGETS GTK3 ZLIB

Important settings:
   value of $EMACSLOADPATH:
   value of $EMACSNATIVELOADPATH:
   value of $LC_MONETARY: en_US.UTF-8
   value of $LC_NUMERIC: en_US.UTF-8
   value of $LC_TIME: en_US.UTF-8
   value of $LANG: en_US.UTF-8
   value of $XMODIFIERS: @im=ibus
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Major mode: ELisp/l

Minor modes in effect:
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   font-lock-mode: t
   blink-cursor-mode: t
   buffer-read-only: t
   column-number-mode: t
   line-number-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   temp-buffer-resize-mode: t

Load-path shadows:
/home/matt/.nix-profile/share/emacs/site-lisp/cmake-mode hides 
/home/matt/.config/emacs/elpa/cmake-mode-3.28.1/cmake-mode
~/env/elisp/ol-notmuch hides 
/home/matt/.config/emacs/elpa/ol-notmuch-2.0.1/ol-notmuch
/nix/store/qm3ihp915s71a5sdvg6w7ag5vr295qmi-emacs-packages-deps/share/emacs/site-lisp/site-start 
hides 
/nix/store/m88zm8z7qrby6zlnq32z35nmn89jdzkl-emacs-pgtk-29.3/share/emacs/site-lisp/site-start
/home/matt/.config/emacs/elpa/project-0.10.0/project hides 
/nix/store/m88zm8z7qrby6zlnq32z35nmn89jdzkl-emacs-pgtk-29.3/share/emacs/29.3/lisp/progmodes/project

Features:
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Memory information:
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