bug#70058: 29.3; `Info-search-case-sensitively' errors with "Wrong type argument: stringp, nil" on failed search

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

1. Run Emacs with 'emacs -Q'
2. Press C-h i to open the Emacs Info pages
3. Press S (capital s, aka `Info-search-case-sensitively')
4. In the minibuffer prompt, type "emacs" or "remember"

Observed result:

  Wrong type argument: stringp, nil

is echoed in the echo area.

Expected result:

  Search failed: "abcdr"

is echoed in the echo area.

Additional Information:

This happens for searches on any string for which there is
*at least one* case-insensitive match. For example, the string "emacs"
(a case sensitive match would yield 0 results, because the correct
casing is "Emacs"), the string "remember" (the correct casing on the top-level
info page is "Remember").


In GNU Emacs 29.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.20,
 cairo version 1.16.0) of 2024-03-25 built on bos03-amd64-034
Repository revision: 73d7d08f3f07a68b198e5ba230a474ba019e6a8a
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12201001
System Description: Ubuntu 22.04.4 LTS

Configured using:
 'configure --prefix=/snap/emacs/current/usr --with-x-toolkit=gtk3
 --without-xaw3d --with-modules --with-cairo
 --with-native-compilation=aot --without-pgtk --with-xinput2
 --with-tree-sitter --with-json
 'CFLAGS=-isystem/build/emacs/parts/emacs/install/usr/include
 -isystem/build/emacs/parts/emacs/install/usr/include/x86_64-linux-gnu
 -isystem/build/emacs/stage/usr/include -O2'
 'CPPFLAGS=-isystem/build/emacs/parts/emacs/install/usr/include
 -isystem/build/emacs/parts/emacs/install/usr/include/x86_64-linux-gnu
 -isystem/build/emacs/stage/usr/include'
 'LDFLAGS=-L/build/emacs/parts/emacs/install/lib
 -L/build/emacs/parts/emacs/install/usr/lib
 -L/build/emacs/parts/emacs/install/lib/x86_64-linux-gnu
 -L/build/emacs/parts/emacs/install/usr/lib/x86_64-linux-gnu
 -L/build/emacs/stage/usr/lib''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER X11 XDBE XIM XINPUT2 XPM
GTK3 ZLIB

Important settings:
  value of $LANG: de_DE.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Group

Minor modes in effect:
  gnus-undo-mode: t
  shell-dirtrack-mode: t
  erc-services-mode: t
  erc-ring-mode: t
  erc-notifications-mode: t
  erc-netsplit-mode: t
  erc-menu-mode: t
  erc-list-mode: t
  erc-irccontrols-mode: t
  erc-keep-place-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  erc-scrolltobottom-mode: t
  erc-imenu-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-bufbar-mode: t
  erc-track-mode: t
  erc-match-mode: t
  erc-autojoin-mode: t
  erc-autoaway-mode: t
  recentf-mode: t
  pixel-scroll-precision-mode: t
  minibuffer-depth-indicate-mode: t
  global-whitespace-mode: t
  global-goto-address-mode: t
  goto-address-mode: t
  global-auto-revert-mode: t
  fido-vertical-mode: t
  icomplete-vertical-mode: t
  icomplete-mode: t
  fido-mode: t
  erc-networks-mode: t
  desktop-save-mode: t
  windmove-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  column-number-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


Features:
(shadow sort gnus-cite mail-extr emacsbug nndraft nnmh nnfolder utf-7
network-stream nsm gnus-agent gnus-srvr gnus-score score-mode nnvirtual
gnus-msg nntp gnus-cache display-line-numbers org-element org-persist
org-id org-refile avl-tree generator oc-basic ol-eww eww url-queue
mm-url ol-rmail ol-mhe ol-irc ol-info ol-gnus nnselect gnus-art mm-uu
mml2015 mm-view mml-smime smime gnutls dig gnus-sum shr pixel-fill
kinsoku url-file svg dom gnus-group gnus-undo gnus-start gnus-dbus
gnus-cloud nnimap nnmail mail-source utf7 nnoo gnus-spec gnus-int
gnus-range message yank-media puny rfc822 mml mml-sec epa derived epg
rfc6068 epg-config mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader gnus-win ol-docview doc-view jka-compr
image-mode exif dired dired-loaddefs ol-bibtex bibtex ol-bbdb ol-w3m
ol-doi org-link-doi org ob ob-tangle ob-ref ob-lob ob-table ob-exp
org-macro org-src ob-comint org-pcomplete org-list org-footnote
org-faces org-entities noutline outline ob-emacs-lisp ob-core ob-eval
org-cycle org-table ol org-fold org-fold-core org-keys oc org-loaddefs
find-func cal-menu calendar cal-loaddefs org-version org-compat org-macs
tramp-cache time-stamp tramp-sh tramp tramp-loaddefs trampver
tramp-integration files-x tramp-compat shell parse-time iso8601
disp-table erc-services erc-ring erc-desktop-notifications notifications
dbus xml erc-nicks color erc-netsplit erc-menu erc-list erc-goodies
erc-imenu imenu erc-pcomplete pcomplete comint ansi-osc ansi-color
erc-button erc-fill erc-stamp erc-status-sidebar erc-track erc-match
erc-join erc-autoaway leuven-dark-theme recentf tree-widget pixel-scroll
cua-base ring mb-depth whitespace goto-addr thingatpt autorevert
filenotify icomplete erc format-spec erc-backend erc-networks erc-common
erc-compat compat erc-loaddefs desktop frameset sendmail rfc2047 rfc2045
ietf-drums gnus nnheader gnus-util text-property-search time-date
mail-utils range mm-util mail-prsvr cus-edit pp cus-load wid-edit
windmove xdg site-start comp comp-cstr warnings icons rx cl-extra
help-mode erc-autoloads info compat-autoloads markdown-mode-autoloads
package browse-url url url-proxy url-privacy url-expand url-methods
url-history url-cookie generate-lisp-file url-domsuf url-util mailcap
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
password-cache json subr-x map byte-opt gv bytecomp byte-compile
url-vars cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren
electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode 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 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
theme-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 dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 379080 22423)
 (symbols 48 29314 3)
 (strings 32 102505 3453)
 (string-bytes 1 3242924)
 (vectors 16 54131)
 (vector-slots 8 958101 26396)
 (floats 8 525 728)
 (intervals 56 588 89)
 (buffers 984 17))