If you select "Yes" to "Is this loan a home equity line of credit or a loan you've ever refinanced?" you should be able to move forward with that entry left blank.
Please enter the original loan's 1098 first and select "Yes" to "Was this loan paid off or refinanced with a different lender in 2018?"
Next, enter the 1098 for the HELOC.
Entering $1 would most likely be inconsequential, but it shouldn't be necessary.