Fixed one possible array  out of bounds issue.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by:  isakov-sl@bk.ru
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15673 6f19259b-4bc3-4df7-8a09-765794883524