[confirm]Herald of Anguish, no mana spent for normal casting

[DivideBy0]

During one of my matches I noticed I could normal cast Herald of Anguish without spending any mana after using Dispel to counter an opponent Counterspell. I've attached a save that allows to replicate the issue:

- Normally cast Herald of Anguish;
- Dispel the opponent Counterspell;
- Herald of Anguish will appear on the field even if no mana has been spent to cast it.

[Aswan jaguar]

Improvise ability in general doesn't charge mana for normal casting. (tested in public version)