archive: Handle open failure
archive: Handle open failure

If gvfs_archive_open fails, libarchive immediately calls
gvfs_archive_close which causes a crash due to calling g_object_unref on
the NULL stream.

https://bugzilla.gnome.org/show_bug.cgi?id=589028

gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs