bug#42801: 26.3; customize-apropos shows bogus State buttons after saving

[Szunti]

After deleting user-emacs-directory (because can't save custom variables
with -Q), started emacs and did the following:

1) M-x customize-apropos RET inhibit RET
2) Toggled Inhibit Startup Screen's value:
Stepped with TAB-s to Inhibit Startup Screen's arrow, RET to open the
details, another TAB onto Toggle button and RET
3) Then typed C-x C-s, confirmed with yes RET

After this the customization buffer refreshed and all options despite
closed, got a State button with STANDARD value.

S-TAB thrice to get onto the State button of the previous option
(Inhibit Startup Echo Area Message) and after RET on the State button,
the echo area tells,

Symbol’s function definition is void: nil

In GNU Emacs 26.3 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.20)
of 2020-05-19 built on felixonmars2
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Arch Linux

Recent messages:
Change the state of this item.
widget-apply: Symbol’s function definition is void: nil
Show or hide rest of the documentation.
Hide or show this option.
Change the state of this item.
user-error: Canceled
Show or hide rest of the documentation.
Create customization buffer for this group.
Show the value of this option.
Change the state of this item.
widget-apply: Symbol’s function definition is void: nil
Configured using:
'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
--localstatedir=/var --with-x-toolkit=gtk3 --with-xft --with-wide-int
--with-modules 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fno-plt'
CPPFLAGS=-D_FORTIFY_SOURCE=2
LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB
NOTIFY ACL GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD LCMS2

Important settings:
value of $LC_TIME: C
value of $LANG: hu_HU.utf8
locale-coding-system: utf-8-unix

Major mode: Custom

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
line-number-mode: t
transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv dired dired-loaddefs format-spec rfc822 mml
mml-sec password-cache epa derived epg epg-config gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils apropos cus-edit easymenu cus-start
cus-load wid-edit cl-loaddefs cl-lib elec-pair time-date mule-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame 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 minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 120540 10887)
(symbols 48 21950 1)
(miscs 40 503 405)
(strings 32 32148 1208)
(string-bytes 1 840406)
(vectors 16 15666)
(vector-slots 8 518108 7434)
(floats 8 61 152)
(intervals 56 448 2)
(buffers 992 15))