Summary / Title: pillage unit disapear when AI change outpost to city


Description: I was pillaging an outpost with 2 scouts and the AI decide to create a city there and my army just disapear with no warning or notification and no battle either. I heard some peoples in my chat who got the same issue but with a much larger army.


Steps to Reproduce: 

- pillage an outpost

- have the AI create a city there or attach the outpost to a city