ToME: the Tales of Maj'Eyal

If you put your alchemist on AI control (by controlling your golem, for example), you get an infinite number of these errors:

Eridan 5269 tactical ai talents testing Shockwave Bomb T_SHOCKWAVE_BOMB
Lua Error: /data/talents/spells/explosives.lua:194: attempt to index global 'ammo' (a nil value)
At [C]:-1
At /data/talents/spells/explosives.lua:194
At (tail call):-1
At /mod/ai//tactical.lua:17
At (tail call):-1
At /mod/ai//tactical.lua:272
At (tail call):-1
At /mod/ai//party.lua:34
At (tail call):-1
At (tail call):-1
At /mod/class/NPC.lua:47 act
At /engine/GameEnergyBased.lua:73 tick
At /engine/GameTurnBased.lua:44 tick
At /mod/class/Game.lua:655

Oops, no, turns out to be any attempt to use Shockwave Bomb (including from the AI) that runs into problems.

Thanks for finding that, (untested) fix attached. Can you apply it and check?

That fixes all of the crashes I could find, and everything seems to work.