bug#8920: 24.0.50; Calendar raises error with #included diary file

[Stephen Berman]

1. Let the file ~/diary consist of the line between start and end:
-----start
#include "~/test"
end------

2. Let ~/test be readable; it's content is irrelevant (can be empty).

3. Let ~/.emacs consist of the lines between start and end:
-----start
(add-hook 'find-file-hook
          (lambda () (set-window-buffer (selected-window)
                                        (set-buffer (current-buffer)))))

(custom-set-variables
 '(calendar-mark-diary-entries-flag t)
 '(calendar-today-visible-hook (quote (calendar-mark-today)))
 '(diary-list-entries-hook (quote (diary-include-other-diary-files)))
 '(diary-mark-entries-hook (quote (diary-mark-included-diary-files))))
end------

4. Invoke emacs (without -Q)

5. Type `M-x calendar RET'
=> Wrong type argument: number-or-marker-p, nil
The Calendar is displayed in the lower window, but today's date is not
marked, and the cursor is at the beginning of the buffer.

Here is the backtrace from entering the debugger on error:

backtrace
Description: backtrace

When I repeat the above recipe through step 4, then instrument the
lambda expression in .emacs for edebugging, then invoke the Calendar and
step through the lambda sexp, the Calendar first appears, then its
window is occupied by the diary buffer, then by the buffer of ~/test,
and finally by the diary again.  No error is raised, and when I switch
to the *Calendar* buffer, today's date is shown marked.


In GNU Emacs 24.0.50.1 (i686-suse-linux-gnu, GTK+ Version 2.20.1)
 of 2011-06-04 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10800000
configured using `configure  '--without-toolkit-scroll-bars' 'CFLAGS=-g -O2 
-fno-optimize-sibling-calls''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t