findNextEmptyCell doesn't work if we just entered a space

[bcopeland]

Space doesn't work as a navigational key because we always call navNext() after type which looks for the first empty cell, but typing a space clears the current cell. To fix we'd need to make sure navNext starts the search at x+1 (or y+1), but only when typing, not when, e.g. tabbing to next entry.