bug#59750: 29.0.60; pcomplete completion error

bug#59750: 29.0.60; pcomplete completion error

[Daniel Mendler]

1. M-x eshell
2. Enter `ls * `
3. Press TAB (completion-at-point) -> wrong-type-argument error

Debugger entered--Lisp error: (wrong-type-argument stringp ("file1"
  "file2" ...))
  pcomplete-match("\\`--[^=]+=\\(.*\\)" 0)
  pcomplete-here-using-help("ls --help")
  pcomplete/ls()
  pcomplete-completions()
  pcomplete-completions-at-point()
  completion--capf-wrapper(pcomplete-completions-at-point all)
  completion-at-point()
  funcall-interactively(completion-at-point)
  command-execute(completion-at-point)

In GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0, Xaw scroll bars) of 2022-11-30 built on projects
Repository revision: dc0f2ec2dbf101a7b755db106ff0e53cbca3b23c
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

Configured using:
 'configure --prefix=/home/user/emacs/install --with-json
 --with-native-compilation --with-x-toolkit=athena --without-dbus
 --without-selinux --without-threads --without-gsettings --with-cairo'

Configured features:
CAIRO FREETYPE GIF GLIB GMP GNUTLS HARFBUZZ JPEG JSON LIBXML2 MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 TIFF
TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XINPUT2 XPM LUCID ZLIB

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

Major mode: Eshell

Minor modes in effect:
  shell-dirtrack-mode: t
  eshell-prompt-mode: t
  eshell-hist-mode: t
  eshell-pred-mode: t
  eshell-cmpl-mode: t
  eshell-proc-mode: t
  eshell-arg-mode: t
  tooltip-mode: t
  global-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 pcmpl-unix
em-unix em-term term disp-table shell ehelp em-script em-prompt em-ls
em-hist em-pred em-glob em-extpipe em-cmpl em-dirs esh-var pcomplete
comint ansi-osc ansi-color ring em-basic em-banner em-alias esh-mode
eshell esh-cmd generator esh-ext esh-opt esh-proc esh-io esh-arg
esh-module esh-groups esh-util cus-edit pp cus-start cus-load wid-edit
cl-loaddefs comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv
cl-extra help-mode bytecomp byte-compile cl-lib files-x 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 inotify
dynamic-setting font-render-setting cairo x-toolkit xinput2 x multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 123886 11347)
 (symbols 48 10706 0)
 (strings 32 30136 2166)
 (string-bytes 1 953426)
 (vectors 16 20925)
 (vector-slots 8 414282 12554)
 (floats 8 42 38)
 (intervals 56 270 0)
 (buffers 984 12))