Collectible Card Game Headquarters

The situation:
* I have in play:
** Batterskull
** Sensei's Divining Top
** several lands
* Opponent plays TukTuk Scrapper
* TukTuk resolves, the trigger goes on the stack
* No target has been assigned. When I hover over the the trigger that's on the stack, there's only an arrow pointing from TukTuk to the trigger.
* I bounce Batterskull
* Sensei's Divining Top is destroyed, because it's the only legal target.

Bug: the opponent should have assigned a target when the trigger goes on the stack.

LevelX: Fixed beyond v6