CommonFun.GetUserDefLevel
function CommonFun.GetUserDefLevel(targetUser, element)
  local targetDefLevel = 1
  if targetUser:GetNpcID() ~= 0 then
    if targetUser:GetNatureLv() ~= 0 then
      return targetUser:GetNatureLv()
    end
    local monster = Table_Monster[targetUser:GetNpcID()]
    if monster ~= nil and monster.NatureLevel ~= nil and monster.NatureLevel ~= 0 then
      targetDefLevel = monster.NatureLevel
    end
  end
  targetDefLevel = targetDefLevel + targetUser:GetElementDefUpLevel(element)
  targetDefLevel = math.min(targetDefLevel, 4)
  return targetDefLevel
end