message: Correct Porcelain Tower exception for no foreign trade
diff: @@ -10679,7 +10679,7 @@ int CvPlayer::getNoForeignTradeCount() const
  bool CvPlayer::isNoForeignTrade() const
  {
  - return (getNoForeignTradeCount() > 0 && isHasBuildingEffect((BuildingTypes)PORCELAIN_TOWER));
  + return (getNoForeignTradeCount() > 0 && !isHasBuildingEffect((BuildingTypes)PORCELAIN_TOWER));
  }
  