You can remove it, but you will need to exit the review to do so. Go back to the actual form and click on Edit (or the pencil icon) to make the changes. Then go back through the review - the error should be gone. And are you sure it is a 1099-G - there is no box 12A on a 1099-G; is it a w-2?
If it is a w-2, search for W-2 and use the jump to W-2 link to get back to your form summary screen where you can click Edit. Or search for whatever form it is you need to edit.