Problem adding a new transaction into a posted and paid invoice

Hi Everyone,

I have a voucher that was entered in December 29th, 2015, so the G/L date was 29/12/2015, the supplier was paid in full in 11/01/2016, the invoice was posted to G/L and paid, after a month, someone realized there was an error on the voucher, he decide to add a new transaction into an existing invoice. After adding a transaction into the existing invoice, the status changed from "D" to Blank" and that causes a problem to post into G/L because no amount was entered.

My question, is there a way to prevent changing or adding anything into