#18 Arrow navigation sometimes fails

[Roel Hertoghs]

Arrow navigation can be wrong, especially when the
window is getting focus again, yet not always.

[Roel Hertoghs]

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How to reproduce?
- Select cell (8, 5) (thus, bottom right of a box)
- Press Alt_V to select the menu
- Press escape to get focus back on the puzzle
- Now press left arrow.
One would expect to go to (7,5), yet is sent to (5,3): some
reset that shouldn't take place.