Refine code to fix potential code bug.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14949 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/HiiDatabaseDxe/ConfigRouting.c

@@ -1287,7 +1287,7 @@ IsThisVarstore (
   //
   // If ConfigHdr has name field and varstore not has name, return FALSE.
   //
-  if (Name == NULL && StrStr (ConfigHdr, L"NAME=&") == NULL) {
+  if (Name == NULL && ConfigHdr != NULL && StrStr (ConfigHdr, L"NAME=&") == NULL) {
     return FALSE;
   }