SecurityPkg: SecureBootConfigDxe: Add NULL pointer check

Add SecureBoot NULL pointer check before reference it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chao Zhang <chao.b.zhang@intel.com>
Reviewed-by: Samer El-Haj-Mahmoud <elhaj@hpe.com>
Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>

SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigImpl.c

@@ -2933,7 +2933,7 @@ SecureBootExtractConfigFromVariable (
   //
   // Fix Pk, SecureBootEnable inconsistence
   //
-  if ((*SetupMode) == USER_MODE) {
+  if ((SetupMode != NULL) && (*SetupMode) == USER_MODE) {
     ConfigData->HideSecureBoot = FALSE;
     if ((SecureBootEnable != NULL) && (*SecureBootEnable == SECURE_BOOT_ENABLE)) {
       ConfigData->AttemptSecureBoot = TRUE;