ToME: the Tales of Maj'Eyal

When selecting an empty square with called shot talents they all behave differently

Noggin Knockers doesn't do anything (does not cost a turn, does not go on cooldown)
Kneecapper goes on cooldown and costs a turn
Killshot costs a turn but does not go on cooldown

I think all these talents should behave like Noggin Knockers in this case.

Fix merge request: https://git.net-core.org/tome/t-engine4 ... quests/742

Fix commit: https://git.net-core.org/tome/t-engine4 ... 4d8052ff79

There were a few ways this could have been addressed, but I agree the best solution is for them to behave like Knoggin Knocker. Since Called Shots are handled in such a way that they will only hit the targeted actor, targeting an empty tile is always useless and may as well be prevented. Note this is how multi shots like Knoggin Knocker normally behave, but not how single shots like Kill Shot and Kneecapper normally would. However, in this case, I think it is the best solution.