EMI: Allow resetting actor turn chores

EMI scripts use nil in SetActorTurnChores() to reset the turn chores,
e.g. when Guybrush picks up the hot coal in wed.lua.
EMI: Restart turn chore when changed mid-turn

When the turn chores are changed while an actor is turning the current
chores will be stopped but the new ones won't be started until the turn
direction changes. This can be seen when hitting the run key while
Guybrush is turning.