Функция словаря с BST возвращает вектор

Функция dictionary_select возвращает вектор, который содержит слова, начинающиеся с W. В этом коде dictionary_select появляется сообщение об ошибке. Но я не могу его найти. Кто-нибудь может мне помочь?

#include <iostream>
#include <string>
#include <vector>

using namespace std;

struct tree {
    string data;
    tree *left;
    tree *right;        
};
typedef tree* dictionary;

bool dictionary_ins_word(dictionary & D, const string & W)
{
    if(W == "" || W == " ")
        return false;

    tree* dic;
    dic = new tree;
    dic->data = W;
    dic->left = NULL;
    dic->right = NULL; 
    if(D == NULL) {
         D = dic;     
    }
    else {
        if(W <= D->data)
            dictionary_ins_word(D->left, W);
        else
            dictionary_ins_word(D->right, W);
    }
    return true;
}
bool dictionary_lookup(const dictionary & D, const string & W)
{
    if(W == "" || W == " ")
        return false;
    if(D == NULL)
        return false;
    if(W == D->data)
        return true;
    else if (W < D->data)
        return dictionary_lookup(D->left, W);
    else
        return dictionary_lookup(D->right, W);
}
bool dictionary_is_empty(const dictionary & D)
{
    if(D == NULL)  
        return true; 
    else
        return false;
}
bool dictionary_del_word(dictionary & D, const string & W)
{
    if(!dictionary_lookup(D, W))
        return false;
    if(W < D->data)
        dictionary_del_word(D->left, W);
    else if(W > D->data)
        dictionary_del_word(D->right, W);
    else {
        string item; 
        tree* temp;
        temp = D;
        if(D->left == NULL) {
            D = D->right;
            delete temp;
        }
        else if(D->right == NULL) {
            D = D->left;
            delete temp;
        }
        else {
            while(D->left->right != NULL) 
                D->left = D->left->right;
            item = D->left->data;

            D->data = item;
            dictionary_del_word(D->left, W);
        }
    }
    return true;
}
bool dictionary_min(string & W, const dictionary & D)
{
    dictionary min;

    if(D == NULL)
        return false;
    min = D;
    while(min->left != NULL)
        min = min->left;
    W = min->data;
    return true;     
}
vector <string> dictionary_select(const dictionary & D, const string & W)
{
vector < string > result;
    vector < string > zeroVec;
    string temp;
    zeroVec.push_back("");

    if(D == NULL)
        return zeroVec;
    temp = D->data;    
    size_t found = temp.find(W);
    if(found == 0)
        result.push_back(D->data);
    if(W <= D->data)
        return dictionary_select(D->left, W);
    else
        return dictionary_select(D->right, W);
}

int main()
{
    bool b[5];
    dictionary l;
    string W, str;
    vector <string> vec;

    l = new tree;
    l->data = "berdi";
    l->left = NULL;
    l->right = NULL;
    b[0] = dictionary_ins_word(l, "atas");
    b[1] = dictionary_ins_word(l, "cara");
    b[2] = dictionary_ins_word(l, "ata");
    b[3] = dictionary_ins_word(l, "atax");
    vec = dictionary_select(l, "ata");
    for(int i=0; i<vec.size(); i++) {
        cout << vec[i] << " ";        
    }
    getchar();
    return 0; 
}