Bug in cv::Orb? - opencv

Question

I recently found some very strange behavior in opencv's ORB descriptor.
cv::Mat grey; //greyscale image
std::vector<cv::KeyPoint> keypoints;
cv::Mat descriptors;
cv::ORB detector;
detector(grey,cv::Mat(),keypoints,descriptors);
The above code consistently crashes if given an image containing no potential keypoints (a black image for example) with the error
OpenCV Error: Assertion failed (m.dims >= 2) in Mat, file /Users/user/slave/ios_framework/src/opencv/modules/core/src/matrix.cpp, line 268
I found that to fix the problem I could do the following
cv::Mat grey;
std::vector<cv::KeyPoint> keypoints;
cv::Mat descriptors;
cv::ORB detector;
detector(grey,cv::Mat(),keypoints);
if(keypoints.size() > 0)
{
detector(grey,cv::Mat(),keypoints,descriptors,true);
}
Which first detects keypoints and then generates their descriptors if any keypoints were detected. I am using opencv2 as a .framework on iOS.
Is this a bug in OpenCV? If not, what am I doing wrong? If so, are there any versions in which it is fixed?

Answer 1

I just ran this code
cv::Mat grey = cv::Mat::zeros(100, 100, CV_8UC1);
std::vector<cv::KeyPoint> keypoints;
cv::Mat descriptors;
cv::ORB detector;
detector(grey,cv::Mat(),keypoints,descriptors);
with OpenCV 2.4.1 without problems.
Did you debug into your code to see where exactly the assertion fails?