C++ program terminates due to vector::_M_range_check: __n

when I try and run my program which successfuly compiles i run into this error

ag715@capa:~$  ./RAT C Parts.txt Output-file
terminate called after throwing an instance of 'std::out_of_range'
  what():  vector::_M_range_check: __n (which is 18446744073709551615) >= this->size() (which is 0)
Aborted (core dumped)

through research i believe one of my vectors may be empty. This is how i am adding elements to my vectors

ofstream outputFile;

std::vector<Part> readpartFile(string fileName) //function to read Builders, Customers and Parts text file
{
    std::vector<Part> parts;

    std::ifstream partsList(fileName);

    std::string line;

    while (std::getline(partsList, line))
    {
        line.pop_back(); //removing '.' at end of line
        std::string token;
        std::istringstream ss(line);
        Part part;

        std::getline(ss, token, ':');
        part.partCode = token[0];
        std::getline(ss, part.partName, ':');
        std::getline(ss, token, ':');
        part.minimum = std::stoi(token);
        std::getline(ss, token, ':');
        part.maximum = std::stoi(token);
        std::getline(ss, token, ':');
        part.complexity = std::stoi(token);
        parts.push_back(std::move(part));
    }

    return parts;
    }

The string stream fileName is parsed through the main function as an argument, as such

int main(int argc,char* argv[]){

const string fileName = "Parts.txt";
auto customerVec = readcustomerFile(argv[1]);

  return 0;

I may add also that previously i did not use command line arguments and the program runs fine. Looking at my readFile functions, can anyone confirm if i am adding to the vector properly or if i am using the correct variables?