Feature Description tutorial not working opencv - c++

Question

I tried the tutorial about feature description on opencv.com and the program crashes with the error:
Debug assertion failed , Expression: vector iterator outside range
in the line_
detector.detect(img_1, keypoints_1);
I'm using OpenCV 2.4.11, with Visual Studio 2010, and I'm linking to opencv_<module>2411d.lib libraries in library directory C:\opencv\build\x86\vc10\lib
The code is here :
#include <iostream>
#include <stdio.h>
#include <opencv2\core\core.hpp>
#include <opencv2\features2d\features2d.hpp>
#include <opencv2\highgui\highgui.hpp>
#include <opencv2\nonfree\features2d.hpp>
#include <opencv2\legacy\legacy.hpp>
using namespace cv;
using namespace std;
int main(int argc, char ** argv)
{
Mat img_1 = imread("3.jpg", CV_LOAD_IMAGE_GRAYSCALE);
Mat img_2 = imread("2.jpg", CV_LOAD_IMAGE_GRAYSCALE);
if (!img_1.data || !img_2.data)
{
cout << " Nu au fost afisate imaginile" << endl;
return -1;
}
int minHessian = 400;
imshow("1.png", img_1);
imshow("2.png", img_2);
SurfFeatureDetector detector(minHessian);
vector<KeyPoint> keypoints_1, keypoints_2;
detector.detect(img_1, keypoints_1);
detector.detect(img_2, keypoints_2);
//-- Step 2: Calculate descriptors (feature vectors)
SurfDescriptorExtractor extractor;
Mat descriptors_1, descriptors_2;
extractor.compute(img_1, keypoints_1, descriptors_1);
extractor.compute(img_2, keypoints_2, descriptors_2);
//-- Step 3: Matching descriptor vectors with a brute force matcher
BFMatcher matcher(NORM_L2);
vector< DMatch > matches;
matcher.match(descriptors_1, descriptors_2, matches);
//-- Draw matches
Mat img_matches;
drawMatches(img_1, keypoints_1, img_2, keypoints_2, matches, img_matches);
//-- Show detected matches
imshow("Matches", img_matches);
waitKey(0);
return 0;
}
and here is when it starts to crash: