NetworkPkg: Fix an error that return type differs from the left one when assigned.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: jiaxinwu <jiaxin.wu@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17921 6f19259b-4bc3-4df7-8a09-765794883524

NetworkPkg/Application/IfConfig6/IfConfig6.c

@@ -127,7 +127,7 @@ SplitStrToList (
   ARG_LIST    *ArgList;
   ARG_LIST    *ArgNode;
 
-  if (*String == L'\0' || *String == NULL) {
+  if (String == NULL || *String == L'\0') {
     return NULL;
   }