imagining we have a name1 and we call user1 = find_user（name1, hearder).given that this function returns NULL in this case, if i want to check user1 is not NULL in an if statement, how should i write it
/*
 * Return a pointer to the user with this name in
 * the list starting with head. Return NULL if no such user exists.
 *
 * NOTE: You'll likely need to cast a (const User *) to a (User *)
 * to satisfy the prototype without warnings.
 */
User *find_user(const char *name, const User *head) {
    // cast a (const User *) to a (User *)
    User *current = (User *) head;

    // Use a while loop chekc if there exists an user with this name in the list given
    while (current != NULL){
        if(strcmp(current->name, name)){
            return current;
        }
        current = current -> next;
    }

    return NULL;
}