I don't know it's a bug or not, and it doesn't always happened, but often. I have put empty city to a city that's belong to my country of course. But another country players can burn that city, and i saw that the empty city still active. So do the deceive tactic. Can u GM check about that ?
don't trust those tactics
empty city mechanism only understood by having empty brain
while deceive as the name clearly explain itself,it's deceiving the user