This came up the other day while playing.
Can you play an action from your hand without a target. For example, the new Imperial card Heavy Fire, a zero cost event reads " Action: A target friendly unit gains either Unit or Blast damage until the end of the phase."
If I have no units in play, can I play the card from my hand, with no target? I am pretty sure the answer is no. However, I was in a tournament the other day, and it got ruled the other way…
My opponent tried to play three events like these in one turn, to dump them from his hand.