Bug#619296: file-roller: Won't delete files in a .xpi

[real name]

Package: file-roller
Version: 2.30.2-2
Severity: normal

Mozilla Firefox addons are archives with a .xpi extension. File-roller can
handle these except when you try to delete files within the archive, you get:

  7-Zip 9.04 beta  Copyright (c) 1999-2009 Igor Pavlov  2009-05-30
  p7zip Version 9.04 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,1 CPU)

  Error: /home/back/Desktop/linkadressen_anzeige-1 (copy).8-fx.xpi is not
  supported archive

  System error:
  Operation not permitted

However, if you rename the file to .zip, then suddenly delete works...

-- System Information:
Debian Release: 6.0.1
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-custom
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages file-roller depends on:
ii  bzip2                  1.0.5-6           high-quality block-sorting file co
ii  gconf2                 2.28.1-6          GNOME configuration database syste
ii  gzip                   1.3.12-9          GNU compression utilities
ii  libc6                  2.11.2-10         Embedded GNU C Library: Shared lib
ii  libgconf2-4            2.28.1-6          GNOME configuration database syste
ii  libglib2.0-0           2.24.2-1          The GLib library of C routines
ii  libgtk2.0-0            2.20.1-2          The GTK+ graphical user interface 
ii  libnautilus-extension1 2.30.1-2squeeze1  libraries for nautilus components 
ii  libpango1.0-0          1.28.3-1+squeeze2 Layout and rendering of internatio
ii  p7zip-full             9.04~dfsg.1-1     7z and 7za file archivers with hig
ii  tar                    1.23-3            GNU version of the tar archiving u

Versions of packages file-roller recommends:
ii  gnome-icon-theme              2.30.3-2   GNOME Desktop icon theme
ii  gvfs                          1.6.4-3    userspace virtual filesystem - ser
pn  rpm2cpio                      <none>     (no description available)

Versions of packages file-roller suggests:
pn  arj                           <none>     (no description available)
ii  binutils                      2.20.1-16  The GNU assembler, linker and bina
ii  cpio                          2.11-4     GNU cpio -- a program to manage ar
pn  lha                           <none>     (no description available)
pn  lzip                          <none>     (no description available)
pn  lzma                          <none>     (no description available)
pn  lzop                          <none>     (no description available)
pn  ncompress                     <none>     (no description available)
pn  rzip                          <none>     (no description available)
pn  sharutils                     <none>     (no description available)
pn  unace                         <none>     (no description available)
pn  unalz                         <none>     (no description available)
pn  unrar | p7zip-rar             <none>     (no description available)
ii  unzip                         6.0-4      De-archiver for .zip files
ii  xz-utils                      5.0.0-2    XZ-format compression utilities
ii  zip                           3.0-3      Archiver for .zip files
pn  zoo                           <none>     (no description available)

-- no debconf information