VC 中的运行时错误，但不在GCC中

i具有此程序，该程序使用GCC完美运行，但在Visual Studio 2017中给出了" vector下标"运行时错误。在使用调试器时，它在功能调用countWords(&v, "hello");上显示了错误。我该如何修复？

#include <iostream>
#include <vector>
using namespace std;
struct Trie {
    int prefixes;
    int words;
    vector<Trie*> edges;
};
typedef Trie vertex;
void initialize(vertex *v)
{
    v->words = 0;
    v->prefixes = 0;
    v->edges.resize(26);
    for (int i = 0; i < 26; i++)
    {
        v->edges[i] = nullptr;
    }
}
void addWord(vertex* v, string word)
{
    if (word == "")
    {
        v->words++;
    }
    else
    {
        v->prefixes++;
        int k = word[0] - 'a' - 1;
        if (v->edges[k] == nullptr)
        {
            v->edges[k] = new Trie;
            initialize(v->edges[k]);
        }
        int word_len = word.length();
        addWord(v->edges[k], word.substr(1, word_len - 1));
    }
}
int countWords(vertex* v, string word)
{
    char k = word[0];
    if (word == "")
        return v->words;
    else if (v->edges[k] == nullptr)
        return 0;
    else
        return countWords(v->edges[k], word.substr(1, word.length() - 1));
}
int main()
{
    Trie v;
    initialize(&v);
    addWord(&v, "hello");
    countWords(&v, "hello");
    cin.get();
}