Hi. Beta4B. Not sure how to reproduce, as it depends on combat odds for invasion.
I invaded the Alterian Home world, Alteria, with 500 Drengin troops. (Gas Attack). They had 2000 defenders. My advantage was 4:1. I had 45 soldiering ability and they had 15. i rolled a 20 to 4 on the 'dice'. Both sides went to 0 - and I was told that my recently conquered planets was suffering an 11% reduction to PQ due to the gas. When I clicked Done, I was returned to the map ...and the Alterians still had the World! And with 10 Billion population!!!! I was charged the 200bc.
I wish I could recreate - I can attack it again, but have been unable to get the same dice roll. Unfortunately in my hurry to capture the screen I closed the window by mistake.
Just wanted to point this out...if , it's the first time I've seen it and obviously the conditions have to be just right to get and exact ratio of losses on both sides to come out to 0. But it happened to me....
on Edit - sems this is not a bug. Thanks all for the answer.