Fix dump_usued segault in debugfs if used without open filesystem

The dump_unused command in debugfs segfaults if used without an open
filesystem:

sor:~ # debugfs
debugfs 1.39 (29-May-2006)
debugfs:  dump_unused
Segmentation fault

Patch (from IBM) below.

Signed-off-by: Matthias Koenig <mkoenig@suse.de>

2 files changed