What is the ruling on selling one's share (*naseeb*) or portion of a house when the exact measure of that share is unknown?

Primary text

If the seller states, 'I sold you my share of this house,' but neither party knows the measure of the share, or if the seller states, 'a share of it' or 'a portion of it,' the sale is invalid due to ambiguity (being unknown). The sale is valid if both parties know the exact measure of the share.