-assert(users != NULL && "users must not be NULL");
-assert(tariffs != NULL && "tariffs must not be NULL");
-assert(admins != NULL && "admins must not be NULL");
-assert(services != NULL && "services must not be NULL");
-assert(corporations != NULL && "corporations must not be NULL");
-assert(traffcounter != NULL && "traffcounter must not be NULL");
+assert(users != nullptr && "users must not be NULL");
+assert(tariffs != nullptr && "tariffs must not be NULL");
+assert(admins != nullptr && "admins must not be NULL");
+assert(services != nullptr && "services must not be NULL");
+assert(corporations != nullptr && "corporations must not be NULL");
+assert(traffcounter != nullptr && "traffcounter must not be NULL");