In reserve_sparse_super2_last_group, the old_desc check should only be
performed if ext2fs_super_and_bgd_loc2() gave us a location -- a
return value of 0 means that there is no old-style GDT block.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>