Треды не меняют значения переменных объекта

#include <Windows.h>
#include <stdio.h>
#include <vector>
 
class CustomParam {
public:
    DWORD m_sum;
    DWORD m_upper;
 
    CustomParam(DWORD sum, DWORD upper) :
        m_sum(sum),
        m_upper(upper)
 
    {}
};
 
 
DWORD WINAPI Summation(_In_ LPVOID Param)
{
    CustomParam &par = *(CustomParam*)Param;
 
    for (DWORD i = 0; i <= par.m_upper; ++i)
    {
        par.m_sum += i;
    }
 
    return 0;
}
 
const size_t AMOUNT_OF_THREADS = 10;
 
int main(int argc, char *argv[])
{
    DWORD currUpper = 5;
 
    std::vector<DWORD> ThreadIds(AMOUNT_OF_THREADS, 0);
    std::vector<HANDLE> ThreadHandles(AMOUNT_OF_THREADS, nullptr);
    std::vector<CustomParam> Params;
 
 
    for (size_t i = 0; i < ThreadHandles.size(); ++i, ++currUpper)
    {
        Params.emplace_back(0, currUpper);
 
        ThreadHandles[i] = CreateThread(NULL, 0, Summation, &(Params[i]), CREATE_SUSPENDED, &(ThreadIds[i]));
 
        if (ThreadHandles[i] = NULL)
        {
            MessageBox(NULL, L"Error creating thread!", L"Error", MB_HELP | MB_OK);
            abort();
        }
    }
 
    for (auto &handle : ThreadHandles)
    {
        ResumeThread(handle);
    }
 
    WaitForMultipleObjects(ThreadHandles.size(), ThreadHandles.data(), TRUE, INFINITE);
 
    for (size_t i = 0; i < ThreadHandles.size(); ++i)
    {
        CloseHandle(ThreadHandles[i]);
    }
 
    for (auto &par : Params)
    {
        printf("Sum = %d\n", par.m_sum);
    }
 
 
    system("pause");
    return 0;
}

std::vector<CustomParam> Params;
//на
std::vector<CustomParam> Params(AMOUNT_OF_THREADS, CustomParam(0,0));
 
/* и */
 
Params.emplace_back(0, currUpper);
//на
Params[i] = CustomParam(0, currUpper);