bug#17560: 24.4.50; wrong type argument if rmail-delete-after-output set

[Ken Olum <kdo@cosmos.phy.tufts.edu>]

Under a recent change, rmail-delete-forward takes an optional repeat
count.  If not specified, the count defaults to nil, giving an error.
This function is called with no arguments in several places including
rmail-output (if rmail-delete-after-output is set).


emacs -Q
M-X rmail
set rmail-delete-after-output to t
press "o"
Give output filename
Get error: Wrong type argument: number-or-marker-p, nil

In GNU Emacs 24.4.50.2 (x86_64-unknown-linux-gnu, X toolkit, Xaw scroll bars)
 of 2014-05-22 on cosmos
Repository revision: 117139 eggert@cs.ucla.edu-20140522164035-y1m18x4smoxvgy58
Windowing system distributor `The Cygwin/X Project', version 11.0.10903000
System Description:	Ubuntu 12.04.4 LTS

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

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

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x r e p o r t - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
delete-backward-char: Text is read-only

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 time-date tooltip
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
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
inotify dynamic-setting font-render-setting x-toolkit x multi-tty emacs)

Memory information:
((conses 16 75357 6383)
 (symbols 48 17734 0)
 (miscs 40 37 152)
 (strings 32 11042 3962)
 (string-bytes 1 287633)
 (vectors 16 9192)
 (vector-slots 8 374109 11495)
 (floats 8 68 264)
 (intervals 56 190 4)
 (buffers 960 11)
 (heap 1024 38120 1325))