Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  string-match("\\`hlist_node\\'" nil)
  imenu-find-default(#("hlist_node" 0 10 (fontified t face font-lock-type-face)) (("*Rescan*" . -99) (nil)))
  imenu--completion-buffer((("*Rescan*" . -99) nil) nil)
  imenu-choose-buffer-index()
  byte-code("\300 C\207" [imenu-choose-buffer-index] 1)
  call-interactively(imenu record nil)
  command-execute(imenu record)
  counsel-M-x-action("imenu")
  ivy-call()
  ivy-read("M-x " ("imenu-list-refresh" "toggle-debug-on-error" "calendar" "org-mode" "counsel-linux-app" "toggle-input-method" "magit-blame" "magit-log" "hide-ifdef-mode" "counsel-etags-update-tags-force" "calc" "calculator" "clang-format-buffer" "asm-mode" "makefile-mode" "counsel-etags-list-tag-in-current-file" "imenu-list-show-noselect" "imenu-add-menubar-index" "imenu-list-show" "s" "cd" "5x5" "arp" "dbx" "dig" "erc" "ert" "eww" "ftp" "gdb" "irc" "hide-ifdefs" "ede" "jdb" "lsp" "man" "mpc" "pdb" "pwd" "rsh" "sdb" "xdb" "diff" "dirs" "ffap" "gnus" "grep" "help" "ielm" "info" ...) :predicate counsel--M-x-externs-predicate :require-match t :history counsel-M-x-history :action counsel-M-x-action :keymap (keymap (67108908 . counsel--info-lookup-symbol) (67108910 . counsel-find-symbol)) :initial-input nil :caller counsel-M-x)
  counsel-M-x()
  funcall-interactively(counsel-M-x)
  call-interactively(counsel-M-x nil nil)
  command-execute(counsel-M-x)

GNU Emacs 26.3
Copyright (C) 2019 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GNU Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING.