+1 to a previously reported bug, but also providing a recipe to
reproduce.

emacs -Q
C-h C-a (about page)
move the cursor to the first link ('GNU Emacs') and wait a second. The
error 'eldoc
error: (void-function eldoc-documentation-function-default)' will appear
in the minibuffer.

In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8)
 of 2014-10-20 on lpowers-tp430
Windowing system distributor `The X.Org Foundation', version 11.0.11501000
System Description:    Ubuntu 14.04.1 LTS

Configured using:
 `configure --with-tiff=no'

Configured features:
XPM JPEG GIF PNG SOUND GSETTINGS NOTIFY LIBXML2 FREETYPE XFT ZLIB

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

Major mode: Fundamental

Minor modes in effect:
  global-smart-tab-mode: t
  global-whitespace-mode: t
  delete-selection-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t

Recent input:
C-h C-a C-p M-f M-f C-f M-x r e p o r <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
eldoc error: (void-function eldoc-documentation-function-default) [3 times]

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message dired format-spec
rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util help-fns mail-prsvr mail-utils eieio byte-opt
bytecomp byte-compile cconv eieio-core finder-inf package epg-config
kivy-mode smart-tab easy-mmode disp-table whitespace edmacro kmacro
cl-loaddefs cl-lib delsel time-date tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese hebrew greek romanian slovak czech european ethiopic
indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple
abbrev minibuffer 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 make-network-process
gfilenotify dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 101609 4619)
 (symbols 48 21419 0)
 (miscs 40 112 121)
 (strings 32 20046 4723)
 (string-bytes 1 581429)
 (vectors 16 14164)
 (vector-slots 8 433697 2106)
 (floats 8 80 271)
 (intervals 56 231 0)
 (buffers 976 12)
 (heap 1024 19340 1209))