Self employed

I am using Turbo Tax Deluxe.  The error window pointing out line 27b will not let me delete the zero.  
I didn't enter anything regarding an Energy Efficient Commercial Building Deduction as I was going through the process of entering all my information into Turbo Tax the first time through.  I only got an error message when running Federal Review near the end.  That's when the pop up showed a zero on line 27b.
How can I go back in and delete the zero on Line 27b?
Again, I am using the Deluxe version.