If the IRS is rejecting your tax return even with a 0 (zero) entered for the 2017 AGI then you have no choice but to print and mail the 2018 tax return. The 2017 AGI is not required with a mailed tax return since you have to physically sign and date the tax return before mailing.
See this TurboTax support FAQ for printing a tax return for mailing when using the online editions - https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online
