Ok. It is ok to answer -0- in that case. Line 5 of Schedule A, Itemized Deductions reports State and local taxes.
People that received a 2018 state refund are taxed on all or a portion of the state and local taxes that they reported when itemizing deductions. Since you did not receive any benefit from state and local taxes in the 2018 reporting, then any state refund from 2018 is not taxable.