在二进制搜索树中查找元素时才能工作

当我向我的BST发送一个查询以返回一个t/f值时，是否找到了这个元素，它在正确的情况下正常工作，但是当元素不在BST中时，它会导致延迟的崩溃。

我难以解出这道题的疑惑

.cpp

bool BinarySearchTree::find(std::string title){

    if (root == NULL)
        return 0;

    return findHelper(root,title);
}

bool BinarySearchTree::findHelper(Node* current, std::string title){

    if (current->title.compare(title) == 0)
        return 1;

    if (current->title.compare(title) < 0)
        findHelper(current->left, title);
    else
        findHelper(current->right, title);

    return 0;
}
main

if (select == 4) {

            bool x;

            string s;

            cout << "Enter Title: " << endl;

            cin.ignore();
            getline(cin, s);

            x = t.find(s);
            if (x)
                cout << "found" << endl;
            else
                cout << "unfound" << endl;

            printMenu();

            cout << "Enter Choice: ";

            cin >> select;

}

谢谢。