Battlemod: fix lua error when act.action is nil

Occurs from status effect generating aoes, like Graupel Formations.
I'm open to suggestions whether to assign a generic action to this like 'AOE' so it's not just blank, but I can't really think what to call the effect. 
But what it shows up as isn't so bad, although the double spacing in there is a little weird.

Graupel Formation   -> {2} Snicky, Garuda (Frost)