I see. Arctic Snake: I would interpret that you can't spend the target lock since there are no dice to reroll. But if it ends up being ruled that you can spend a focus token to change no [focus] results, there's nothing stopping you from spending a target lock to reroll any of your zero dice.
At the risk of sounding like a broken roecord, spending a token when you're not doing anything just smacks of taking advantage of a loop hole to me.