smackfs: Added check catlen

  If the catlen is 0, the memory for the netlbl_lsm_catmap
  structure must be allocated anyway, otherwise the check of
  such rules is not completed correctly.

Signed-off-by: Denis Arefev <arefev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>