Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  string-match("\\([^.]+\\)\\." nil)
  byte-code("Æ!ƒ1
  Info-find-node-2("/usr/local/info/emacs" nil t)
  Info-find-node("/usr/local/info/emacs" nil t)
  byte-code("„!
  signal(error ("No such node or anchor: elisp(Declaring Functions)"))
  error("No such node or anchor: %s" "elisp(Declaring Functions)")
  byte-code("Æ!ƒ1
  Info-find-node-2("/usr/local/info/emacs" "elisp(Declaring Functions)" nil)
  Info-find-node("emacs" "elisp(Declaring Functions)")
  Info-goto-node("(emacs)elisp(Declaring Functions)")
  info("(emacs)elisp(Declaring Functions)")
  apply(info "(emacs)elisp(Declaring Functions)")
  help-do-xref(1624 info ("(emacs)elisp(Declaring Functions)"))
  help-button-action(#<marker (moves after insertion) at 1632 in *Help*>)
  push-button(1632)
  call-interactively(push-button nil nil)