CVE-2019-19624: Out-of-bounds Read

An out-of-bounds read was discovered in OpenCV Specifically, variable coarsest_scale is assumed to be greater than or equal to finest_scale within the calc()/ocl_calc() functions in dis_flow.cpp. However, this is not true when dealing with small images, leading to an out-of-bounds read of the heap-allocated arrays Ux and Uy.