The guy's contract is not valid.
I'm not subscribed to GLOBEX so I cannot request ES. Also, you cannot use SMART as an exchange for Futures, Futures Options, or Commodities, Bonds, etc... SMART is only for stocks and options.
Here is a proper contract for a futures security. Also, you must set the contract "include Expired" because it's 2019 and you're requesting an expired contract.
ibFutures = ib.Handle.createContract;
ibFutures.symbol = 'CL';
ibFutures.secType = 'FUT';
ibFutures.lastTradeDateOrContractMonth = '201812';
ibFutures.includeExpired = true;
ibFutures.exchange = 'NYMEX';
ibFutures.primaryExchange = 'NYMEX';
ibFutures.currency = 'USD';
Now that you have a proper contract, you need to setup the proper request days, you're requesting 20 days of history from today, but again, it's 2019. Either set the current day to Dec 2018 or do as I did -500 days.
currentdate = today;
startDate = daysadd(currentdate,-500,bizDayConvention);
endDate = daysadd(currentdate,-1,bizDayConvention);
Finally run the code
histTradeData = history(ib,ibFutures,startDate,endDate)
This is using the latest stable API 9.72 from IB on R2019a.