Add logic to validate variable before use it.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Jiewen Yao <jiewen,yao@intel.com>
Reviewed-by: Michael D. Kinney <michael.d.kinney@intel.com>
 

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13323 6f19259b-4bc3-4df7-8a09-765794883524
2 files changed