Collectible Card Game Headquarters

Describe the Bug:
Icy Prison can be cast with no creature on battlefield.

Which card did behave improperly?
Icy Prison

Which update are you using? (date, name)Which type? (duel, gauntlet, sealed deck)
Manalink dev 778ccb5 version - duel

What exactly should be the correct behavior/interaction?
Icy Prison can't be cast with no creature on battlefield.

Are any other cards possibly affected by this bug?
-

Perfectly legal, since it's not an Aura. The trigger will fail at anouncement since it doesn't have a legal target, so the AI usually shouldn't cast it when the human player doesn't have a targetable creature. (Looks like it probably will, and Journey to Nowhere too.)

I managed to mess it in my mind as an aura, I can't even blame AI for confusing me by playing it with no creature either it's all my mess.