c++ Unhandled exception: System.NullReferenceException - c++

Question

i'm trying to get process name from Win32_Processor soo i create function ProcessNameInfo.
my code is :
void ProcessNameInfo(string nameoption, String^ hardwareClass, String^ propertyNname)
{
ManagementObjectSearcher^ searcher = gcnew ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM " + hardwareClass);
ManagementObjectCollection^ collection = searcher->Get();
for each (ManagementObject^ object in collection)
{
String ^ s = object[propertyNname]->ToString();
CString str3(s);
const TCHAR* x = (LPCTSTR)str3;
char szString[MAX_LENGTH];
size_t nNumCharConverted;
wcstombs_s(&nNumCharConverted, szString, MAX_LENGTH,
x, MAX_LENGTH);
std::string HardwareInfo = szString;
std::transform(HardwareInfo.begin(), HardwareInfo.end(), HardwareInfo.begin(), [](char ch) {
return ch == ' ' ? '_' : ch;
});
file << "\"" << nameoption << "\": \"" << HardwareInfo << "\"," << endl;
}
}
in the main i call this function like this :
ProcessNameInfo("Processor", "Win32_Processor", "Name");
for some devices it's working but in another devices i get error Unhandled exception:
System.NullReferenceException object reference not set to an instance of an object in ProcessNameInfo(basic_string<char\,std::char_traites<char>\,std::allocator<char> >* nameoption, String hardwareClass, String propertyNname) in main() _mainCRTStartup()