[21.2]: msb breaks Buffers/Frames menu

[Marshall, Simon]

In GNU Emacs 21.2.1 (sparc-sun-solaris2.6, GNU/LessTif Version 2.1
Release 0.93.3)
 of 2002-03-21 on ashanti
configured using `configure  --prefix=/rvcarma/marshals/slash/usr/local
--x-includes=/usr/openwin/include:/rvcarma/marshals/slash/usr/local/incl
ude:/rvcarma/marshals/slash/usr/local/include/X11
--x-libraries=/usr/openwin/lib:/rvcarma/marshals/slash/usr/local/lib:/rv
carma/marshals/slash/usr/local/lib/X11 --with-x-toolkit=motif'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_UK
  value of $LC_CTYPE: en_UK
  value of $LC_MESSAGES: C
  value of $LC_MONETARY: en_UK
  value of $LC_NUMERIC: en_UK
  value of $LC_TIME: en_UK
  value of $LANG: nil
  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:

emacs -q
C-x 5 2 C-h i

so you have 2 frames showing different windows/buffers.

Select Buffers/Frames/<hidden frame> and Emacs raises the frame.  OK.

M-x msb-mode RET

Select Buffers/Frames/<hidden frame> and Emacs barfs:

Debugger entered--Lisp error: (wrong-type-argument framep nil)
  select-frame(nil)
  menu-bar-select-frame()
  call-interactively(menu-bar-select-frame)