Support Object Detection in blank case

[covert-code]

The script must detect and handle object detection more smoothly. Move the object detecter inside mine() from canMine() and allow it to handle the no-sparkle-first-row case more intelligently:

In the case of no sparkles accessible in an unmined mine
=> if there is object detection active, and a second-row square bears a sparkle, mine directly underneath it.

To do this, refresh's model must first be changed to target accessible squares only in OD.