Upon surrender all planets were destroyed

So, the Arceans just ended their war with me and the Navigators and now all of their planets are Dead! The message said they were giving their planets to someone else, but I can't remember who, but instead they are all zeroes. Sure, I a Festron parasite , but still... All those citizens just killed - I needed to infest them.

Previously, I defeated someone else and they turned over their planets to a far off civ intact. Maybe I should go back to fight to the death mode.