Try to enter 0 to see if it clears the error. It might be a holdover from a prior year for a vehicle registration tax or some other kind of personal property tax that you entered and it now has a blank value for this year which is causing the error. It probably has nothing to do with your refinance, unless it is specifically addressing the mortgage interest or real estate tax.
If entering 0 does not work, you can try going back into the Deductions and Credits section of your return, and look for anything that says Needs Review or Not Started. Those might have blank line items because you added them last year and did not input them this year. You can either add values this year or delete them if they are no longer relevant.
