message: Safely delete units during a city flip
diff: @@ -189,7 +189,7 @@ def flipCity(tCityPlot, bConquest, bKillUnits, iNewOwner, lOldOwners = []):
  if not lOldOwners or iOldOwner in lOldOwners:
  if bKillUnits:
  - for unit in units.at(x, y):
  + for unit in units.at(x, y).where(lambda unit: not unit.isCargo()):
  unit.kill(False, iNewOwner)
  pNewOwner.acquireCity(flipCity, bConquest, not bConquest)
  