Fix keypoint bug.
Fix keypoint bug.

* Set keypoint descriptor to zero, bug was introduced when switching to arrays.

openmv/openmv,openmv/openmv,iabdalkader/openmv,openmv/openmv,kwagyeman/openmv,iabdalkader/openmv,iabdalkader/openmv,iabdalkader/openmv,kwagyeman/openmv,openmv/openmv,kwagyeman/openmv,kwagyeman/openmv