ext[234]_get_group_desc never tests the bh argument, and only sets it if it
is passed in; it is perfectly happy with a NULL bh argument.  But, many
callers send one in and never use it.  May as well call with NULL like
other callers who don't use the bh.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>