CommandLineParser crashed (Bug #2471)

If I use wrong syntax then parser is crashed.

For example(main.cpp):

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>

const std::string keys = 
    "{ b | bug  | 42 | it's a bug }" 
    "{ h | help |  |     | help info  }" 
    "{ |  i   | 7   | i - int    }" 
;

int main(int argc, char ** argv)
{
    cv::CommandLineParser parser(argc, argv, keys);

    if (parser.has("help"))
    {
        parser.printMessage();
        return 0;
    }

    int a = parser.get<int>("i");
    int b = parser.get<int>("b");
    std::cout << a << std::endl;
    std::cout << b << std::endl;

    if (!parser.check())
    {
        parser.printErrors();
        return 0;
    }
    return 0;
}