Issue: When an outpost is upgraded into a city any units ransacking the outpost are deleted.

Steps to reproduce:

1. Player 1 starts to ransack player 2's outpost
2. Player 2 upgrades the ransacked outpost into a city

Expected behaviour: Unsure, either units are moved out of hostile territory, returned to capital, or remain in place but are trespassing. It doesn't make much sense that they all just die...