bug#58167: 29.0.50; Loading wallpaper signals an error

[Eli Zaretskii <eliz@gnu.org>]

As per the Subject.

To reproduce:

  emacs -Q
  M-x load-library RET wallpaper RET

I get the same error when I invoke "M-x wallpaper-set RET".

Here's the backtrace from loading wallpaper.el:

Debugger entered--Lisp error: (wrong-type-argument wallpaper-setter nil)
  signal(wrong-type-argument (wallpaper-setter nil))
  (or (and (memq (type-of cl-x) cl-struct-wallpaper-setter-tags) t) (signal 'wrong-type-argument (list 'wallpaper-setter cl-x)))
  (progn (or (and (memq (type-of cl-x) cl-struct-wallpaper-setter-tags) t) (signal 'wrong-type-argument (list 'wallpaper-setter cl-x))) (aref cl-x 2))
  (let ((cl-x (wallpaper--find-setter))) (progn (or (and (memq (type-of cl-x) cl-struct-wallpaper-setter-tags) t) (signal 'wrong-type-argument (list 'wallpaper-setter cl-x))) (aref cl-x 2)))
  wallpaper--find-command()
  (closure (wallpaper-command-args cl-struct-wallpaper-setter-tags t) nil "" (wallpaper--find-command))()
  funcall((closure (wallpaper-command-args cl-struct-wallpaper-setter-tags t) nil "" (wallpaper--find-command)))
  eval((funcall #'(closure (wallpaper-command-args cl-struct-wallpaper-setter-tags t) nil "" (wallpaper--find-command))))
  custom-initialize-reset(wallpaper-command (funcall #'(closure (wallpaper-command-args cl-struct-wallpaper-setter-tags t) nil "" (wallpaper--find-command))))
  custom-declare-variable(wallpaper-command (funcall #'(closure (wallpaper-command-args cl-struct-wallpaper-setter-tags t) nil "" (wallpaper--find-command))) "Executable used by `wallpaper-set' for setting the..." :type (choice (radio (const :tag "gsettings                   (GNOME)" "gsettings") (const :tag "plasma-apply-wallpaperimage (KDE Plasma)" "plasma-apply-wallpaperimage") (const :tag "xfconf-query                (XFCE)" "xfconf-query") (const :tag "pcmanf                      (LXDE)" "pcmanf") (const :tag "pcmanf-qt                   (LXQt)" "pcmanf-qt") (const :tag "swaybg                      (Wayland/Sway)" "swaybg") (const :tag "wbg                         (Wayland)" "wbg") (const :tag "gm                          (X Window System)" "gm") (const :tag "display                  
    (X Window System)" "display") (const :tag "feh                         (X Window System)" "feh") (const :tag "fbsetbg                     (X Window System)" "fbsetbg") (const :tag "xwallpaper                  (X Window System)" "xwallpaper") (const :tag "hsetroot                    (X Window System)" "hsetroot") (const :tag "xloadimage                  (X Window System)" "xloadimage") (const :tag "xsetbg                      (X Window System)" "xsetbg") (const :tag "osascript                   (macOS)" "osascript")) (const :tag "Other (specify)" string) (const :tag "None" nil)) :set wallpaper--set-wallpaper-command :group image :version "29.1")
  eval-buffer(#<buffer  *load*> nil "emacs/trunk/lisp/image/wallpaper.el" nil t)  ; Reading at buffer position 12390
  load-with-code-conversion("emacs/trunk/lisp/image/wallpaper.el" "emacs/trunk/lisp/image/wallpaper.el" nil nil)
  load("emacs/trunk/lisp/image/wallpaper.el" nil nil t)
  load-file("emacs/trunk/lisp/image/wallpaper.el")
  funcall-interactively(load-file "emacs/trunk/lisp/image/wallpaper.el")
  call-interactively(load-file record nil)
  command-execute(load-file record)
  execute-extended-command(nil "load-file" "load-fi")
  funcall-interactively(execute-extended-command nil "load-file" "load-fi")
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)


In GNU Emacs 29.0.50 (build 1964, i686-pc-mingw32) of 2022-09-29 built
 on HOME-C4E4A596F7
Repository revision: a18918df0bd0ddd9c8b05b99c302e26b226af5d3
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure -C --prefix=/d/usr --with-wide-int
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XPM ZLIB

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-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
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils cl-print
byte-opt bytecomp byte-compile cconv debug backtrace find-func cl-extra
cl-seq cl-macs gv xdg subr-x cus-edit pp icons wid-edit cus-start
cus-load thingatpt help-fns radix-tree help-mode cl-loaddefs cl-lib rmc
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel dos-w32 ls-lisp disp-table
term/w32-win w32-win w32-vars term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-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 nadvice seq simple cl-generic
indonesian philippine 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 emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
faces cus-face macroexp files window text-properties overlay sha1 md5
base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads w32notify w32 lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 82982 11891)
 (symbols 48 9337 0)
 (strings 16 25966 2321)
 (string-bytes 1 662724)
 (vectors 16 15015)
 (vector-slots 8 198952 19501)
 (floats 8 40 42)
 (intervals 40 712 108)
 (buffers 896 13))