display of 0 price and no price is same

Hello and thx for this great plugin.

I have a problem with how prices shown in bulk editor.

at the moment display of products with 0 price and no price is same that would be great if the look of both be diffrent. because if accidentaly anyone put 0 price in field the product price will be 0 which means free and no one will be noticed unless they check on front end.
also Im asking in case of leaving field empty and pressing enter make the input value to -1 so the price is removed and no need to enter -1 for removing price.