gnome_url_show_with_env doesn't interpret GNOME_VFS_ERROR_NOT_FOUND error condition

GNOME_VFS_ERROR_NOT_FOUND is returned when you try and open a non-existent file
with gnome_vfs_url_show_with_env()

As some apps (e.g. tomboy in bug #359727) present the message from the GError
to the user, it would be nice to have something other than "Unknown error code:
1" here

http://bugzilla.gnome.org/show_bug.cgi?id=360932

Index: ChangeLog
===================================================================
RCS file: /cvs/gnome/libgnome/ChangeLog,v
retrieving revision 1.498
diff -u -B -r1.498 ChangeLog
--- ChangeLog	26 Sep 2006 17:15:41 -0000	1.498
+++ ChangeLog	15 Oct 2006 16:19:17 -0000
@@ -1,3 +1,7 @@
+2006-10-15  Daniel Drake  <dsd@gentoo.org>
+
+	* libgnome/gnome-url.c: Interpret GNOME_VFS_ERROR_NOT_FOUND (bug #360932)
+
 2006-09-26  Matthew Barnes  <mbarnes@redhat.com>
 
 	* doc/reference/libgnomeui-docs.sgml: Make the API documentation
Index: libgnome/gnome-url.c
===================================================================
RCS file: /cvs/gnome/libgnome/libgnome/gnome-url.c,v
retrieving revision 1.53
diff -u -B -r1.53 gnome-url.c
--- libgnome/gnome-url.c	10 Jul 2006 13:32:20 -0000	1.53
+++ libgnome/gnome-url.c	15 Oct 2006 16:19:17 -0000
@@ -150,6 +150,7 @@
 		break;
 
 	case GNOME_VFS_ERROR_INVALID_URI:
+	case GNOME_VFS_ERROR_NOT_FOUND:
 		g_set_error (error,
 		             GNOME_URL_ERROR,
 			     GNOME_URL_ERROR_VFS,