Strange loading of vc-bzr with additional file-handler

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

I am testing a file handler for sending files to the shell when opening 
them. I do not understand all the bits and pieces there. Though I have 
only defined operation 'insert-file-contents it works well most of the 
time, but suddenly I got the strange traceback below.

Debugger entered--Lisp error: (void-function vc-bzr-state-heuristic)
   vc-bzr-state-heuristic("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   vc-bzr-registered("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   apply(vc-bzr-registered "c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   vc-call-backend(Bzr registered 
"c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   #[(b) " \b 	# \x14... (some byte code here)
   vc-registered("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   apply(vc-registered "c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   (let ((inhibit-file-name-handlers ...) (inhibit-file-name-operation 
operation)) (apply operation args))
   (if done nil (let (... ...) (apply operation args)))
   (unless done (let (... ...) (apply operation args)))
   (let ((done nil) ftype) (when (eq operation ...) (when ... ...) 
(unless ... ... ...)) (unless done (let ... ...)))
   sex-file-handler(vc-registered 
"c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   vc-registered("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   vc-backend("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf")
   #[nil " \b! " [buffer-file-name vc-backend] 2]()
   vc-find-file-hook()
   run-hooks(find-file-hook)
   after-find-file(nil t)
   find-file-noselect-1(#<buffer gimpmode.pdf<2>> 
"c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf" nil nil 
"c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf" (0 203134463))
   find-file-noselect("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf" nil 
nil t)
   ad-Orig-find-file("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf" t)
   (setq ad-return-value (ad-Orig-find-file filename wildcards))
   (let (ad-return-value) (setq ad-return-value (ad-Orig-find-file 
filename wildcards)) ad-return-value)
   find-file("c:/emacs-lisp/gimp-mode-v1.40/gimpmode.pdf" t)
   call-interactively(find-file nil nil)