change-log-version-enabled code needs to test if a file is version controlled

[Robert Marshall]

In GNU Emacs 21.1.1 (i386-msvc-windows98.2222)
 of 2001-10-29 on SWC-MAN-L004
configured using `configure --with-msvc (12.00)'
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: eng
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

If you set
(setq change-log-version-info-enabled t)
and then try add-change-log-entry-other-window on a file that isn't
under version control 
(or where the version control system hasn't been 'emacsed') 

You get the error
vc-find-backend-function: Cannot open load file: vc-nil

As it's trying to determine the version number, I think there needs to
be a test of the result of vc-registered first, or make the variable
buffer local?

  require(vc-nil)
  vc-find-backend-function(nil workfile-version)
  vc-call-backend(nil workfile-version "c:/elisp/.emacs")
  vc-workfile-version("c:/elisp/.emacs")
  change-log-version-number-search()
  add-change-log-entry(nil nil t)
  add-change-log-entry-other-window()
  call-interactively(add-change-log-entry-other-window)

R
-- 
Robert Marshall