bug#8170: vc-dir choking on new bzr status output

[Juanma Barranquero]

>From Bazaar 2.3.0 on, bzr status shows a summary of the shelves:

  C:\emacs\trunk\> bzr status
  modified:
    lisp/ChangeLog
    lisp/image-dired.el
  1 shelf exists. See "bzr shelve --list" for details.

which vc-dir does not understand:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  ewoc-data(nil)
  vc-dir-node-directory(nil)
  vc-dir-update((("../elf exists. See \"bzr shelve --list\" for
details." nil) ("ChangeLog" edited) ("image-dired.el" edited))
#<buffer *vc-dir*>)
  #[(G102203 entries &optional more-to-come) "r Jq\210\306       J\"\210\n?\205'

This happens in 23.3RC and 24.0.50.

    Juanma