Form w2g certain gambling winnings box 18 is empty. Does that box have to be entered?

TurboTax would not allow me to submit my return with this field blank. Please explain why you are telling me to leave it blank if you won't allow me to submit my return because of it?

No, it doesn't. If the box is empty on the actual form, please leave this field blank in TurboTax as well. Do not enter zeros. 

I saw in another question/answer entry that the TurboTax representative said to enter "XXX" and I was forced to do that on my return as well, because TurboTax would not allow me to submit my return with the information being blank on that line. Thoughts?