HDR Imaging - assert failure during merge_mertens (Bug #3939)

According to the HDR-Tutorial: http://docs.opencv.org/trunk/doc/tutorials/photo/hdr_imaging/hdr_imaging.html#hdrimaging
Merge_Mertens does not work.

Example Code:

cv::Mat fusion;
cv::Ptr<cv::MergeMertens> merge_mertens = cv::createMergeMertens();
merge_mertens->process(images, fusion);

Execution results always in the following error:

OpenCV Error: Assertion failed (y == 0 || (data && dims >= 1 && (unsigned)y < (u nsigned)size.p⁰)) in cv::Mat::ptr, file C:\builds\master_PackSlave-win64-vc11- static\opencv\modules\core\include\opencv2/core/mat.inl.hpp, line 750

The bug happens in this line of code (example: 7 images in the vector, crash at image 4):

for(int lvl = 0; lvl < maxlevel; lvl++) {
Mat up;
pyrUp(img_pyr[lvl + 1], up, img_pyr[lvl].size());
img_pyr[lvl] -= up;
}

Images are not huge so memory consumption should not be a problem.