Fiery Conclusion sacrifice target bug

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Fiery Conclusion is very interesting spell: it destroys one creature that you control and deal 5 damage to opponent's creature.

As you can see from game mechanic, this spell need two "choose" parts: choose your "sacrifice target" and choose opponent's "damage target". So you can choose "sacrifice target", but after that cancel choosing of "damage target" and don't use this spell at this turn.

But after that you might want to use this spell again. At this moment you will see very funny bug: spell "remembers" it's sacrifice target from your first choosing. What does it mean?

1) If I use it on creature, cancel casting, use it after when creature is still alive - it kills this creature as it should be (but won't ask me again if I wan't to choose another sacrifice target).
2) I use it on creature, cancel casting, use it after this creature were destroyed - spell deals damage to opponent's creature and... kill no my creatures (it's sacrifice target is dead already ). Important moment: I can't fully use this "half-activated" spell without some creatures on my side - even if it doesn't give me chance to choose one of them.

Funny interaction with Act of Treason: if I choose creature-"traitor" as sacrifice target and it returns to opponent, it will destroyed with activating this spell later even if it is not under my control on activating moment (I did special check of this fact). And if traitor were destroyed already, spell won't destroy anybody as with my creatures at 2).