Fix crash caused by 4 bytes pointer to member in Windows

Author: Qiuwen-chen

src/cpp/orm/binding/MemberPointer.hpp

@@ -43,6 +43,7 @@ void* castMemberPointer(T O::*memberPointer)
         T O::*memberp;
         void* voidp;
     };
+    voidp = nullptr;
     memberp = memberPointer;
     return voidp;
 }