Under the foreign income tax exclusion section for trips to the US, I am getting an error if I enter "0" for the number of days in the US for business.

When entering information about a vacation to the US for personal reasons, not business, I enter the length of the stay in the US in days as "9". Then, it asks how many days were for business and I get an error when I put "0", even though the trip was NOT for business. I believe this is an error in TurboTax that needs to be corrected and I should not have to pay for help.