bug#20347: 25.0.50; `global-subword-mode' breaks ERC

[Mark Karpov]

To reproduce: start emacs with -Q option, then execute `M-x
global-subword-mode', then `M-x erc'. You'll get the following error
message in the minibuffer:

error in process filter: Wrong type argument: integer-or-marker-p, nil

it's impossible to fathom how this minor mode can affect ERC. Note that
I'm using 25.0.50 version of Emacs (compiled from git repository).



In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.2)
 of 2015-04-14 on arch
Windowing system distributor `The X.Org Foundation', version 11.0.11701000
Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB

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

Major mode: iε

Minor modes in effect:
  fci-mode: t
  rainbow-delimiters-mode: t
  flycheck-mode: t
  flyspell-mode: t
  which-function-mode: t
  show-paren-mode: t
  minibuffer-electric-default-mode: t
  ido-ubiquitous-mode: t
  ido-everywhere: t
  global-auto-revert-mode: t
  display-time-mode: t
  delete-selection-mode: t
  smooth-scroll-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  auto-fill-function: do-auto-fill
  auto-fill-mode: 1
  abbrev-mode: t

Recent messages:
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/bridge.el' 
newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-scratch.el'
 newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-references.el'
 newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-compiler-notes-tree.el'
 newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-package-fu.el'
 newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-fontifying-fu.el'
 newer than byte-compiled file
Source file 
`/home/mark/quicklisp/dists/quicklisp/software/slime-2.12/contrib/slime-trace-dialog.el'
 newer than byte-compiled file
Loading /home/mark/quicklisp/slime-helper.elc...done
Starting new Ispell process /usr/bin/aspell with default dictionary...
Thursday, 16 April 2015

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message dired format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils disp-table fill-column-indicator
rainbow-delimiters flycheck-haskell haskell-cabal haskell-utils flycheck
find-func help-mode rx subr-x flyspell ispell mk-visual
solarized-dark-theme solarized dash mk-slime slime-fancy
slime-trace-dialog slime-fontifying-fu slime-package-fu slime-references
slime-compiler-notes-tree slime-scratch slime-presentations bridge
slime-fuzzy slime-fancy-trace slime-fancy-inspector slime-c-p-c
slime-editing-commands slime-autodoc slime-repl slime-parse slime
compile etags xref eieio eieio-core cl-generic arc-mode archive-mode
noutline outline easy-mmode pp comint ansi-color ring hyperspec
thingatpt browse-url slime-autoloads cl-macs mk-scheme mk-prolog mk-org
mk-markdown mk-man mk-magit mk-haskell mk-gnus mk-erc mk-elisp mk-dired
mk-diff mk-cider mk-calendar mk-c mk-abbrev mk-minor-modes which-func
imenu paren minibuf-eldef ido-ubiquitous ido-completing-read+ ido
warnings byte-opt autorevert filenotify time delsel mk-global edmacro
kmacro mk-utils server smooth-scroll bytecomp byte-compile cl-extra seq
cconv cl gv cl-loaddefs pcase cl-lib finder-inf advice help-fns info
easymenu package epg-config 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 cl-preloaded 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 dbusbind gfilenotify dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty emacs)

Memory information:
((conses 16 236206 118868)
 (symbols 48 31985 2)
 (miscs 40 379 1419)
 (strings 32 56579 53440)
 (string-bytes 1 1537744)
 (vectors 16 24665)
 (vector-slots 8 565404 39964)
 (floats 8 279 360)
 (intervals 56 285 109)
 (buffers 976 12)
 (heap 1024 37071 4606))