ext4: fix buffer leak in ext4_expand_extra_isize_ea() on error path

Fixes: de05ca85 ("ext4: move call to ext4_error() into ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 4.17