message: Prevent double improvement degradation
diff: @@ -348,6 +348,7 @@ class Plague:
  CyInterface().addMessage(city.getOwner(), True, iDuration/2, CyTranslator().getText("TXT_KEY_PLAGUE_SPREAD_CITY", ()) + " " + city.getName() + "!", "AS2D_PLAGUE", 0, "", ColorTypes(iLime), -1, -1, True, True)
  for (x, y) in utils.surroundingPlots((city.getX(), city.getY()), 2):
  pPlot = gc.getMap().plot( x, y )
  + if pPlot.getUpgradeProgress() > 0:
  pPlot.setUpgradeProgress(0)
  iImprovement = pPlot.getImprovementType()
  if iImprovement == iTown:
  