bug#14954: 24.3.50; eww doesn't not use browse-url-xdg-open properly?

[Jambunathan K]

0. Install xdg-open
1. Put cursor on inside the URL below.

    http://thread.gmane.org/47B4E3B2.3050402@gmail.com

1. M-x browse-url-xdg-open or M-x browse-url or Left mouse click
   
   See firefox getting launched.

2. M-x eww-browse-with-external-browser

   See following backtrace.

    Debugger entered--Lisp error: (wrong-type-argument stringp nil)
      call-process("xdg-open" nil 0 nil nil)
      browse-url-xdg-open(nil)
      apply(browse-url-xdg-open nil nil)
      browse-url-default-browser(nil)
      eww-browse-with-external-browser()
      call-interactively(eww-browse-with-external-browser record nil)
      command-execute(eww-browse-with-external-browser record)
      execute-extended-command(nil "eww-browse-with-external-browser")
      call-interactively(execute-extended-command nil nil)
      command-execute(execute-extended-command)

I have no fancy customization of browse-url-* options.  Just the
standard defaults on a debian.

In GNU Emacs 24.3.50.24 (i686-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2013-07-26 on debian-6.05
Bzr revision: 113547 rgm@gnu.org-20130726015506-xqc4ksyjl4qxvh8f
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
Important settings:
  value of $LANG: en_IN
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t