LU-4629 mdc: fix issue found by Klocwork Insight tool

LU-4629 mdc: fix issue found by Klocwork Insight tool

Pointer 'mod' checked for NULL at line 160 may be dereferenced at line 208.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I130de2f5b2066b8797e2454d4a603f53b3ffcbef
Reviewed-on: http://review.whamcloud.com/9387
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>