This commit modifies the code logic to avoid passing NULL pointer to function BN_bn2bin(). Cc: Long Qin <qin.long@intel.com> Cc: Ye Ting <ting.ye@intel.com> Cc: Fu Siyuan <siyuan.fu@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu <hao.a.wu@intel.com> Reviewed-by: Qin Long <qin.long@intel.com>