ext4_xattr_destroy_cache() can handle NULL pointer correctly,
so there is no need to check NULL pointer before calling
ext4_xattr_destroy_cache().
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NChengguang Xu <cgxu519@gmx.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>