He vowed to give charity if he recovered the money that was owed to him, and he recovered half of it; does he have to give in charity?

There is someone who was owed a debt and had lost all hope of recovering it, so he vowed to Allah that he would give in charity a certain sum of money if he recovered the money that was owed to him. After that there were some negotiations with the debtor, and the two parties agreed that half of the debt would be waived in return for repayment of the other half. In this case, is the one who made the vow obliged to do anything with regard to his vow? In other words, should he give half of what he vowed, or not give anything at all, because the condition of the vow was not fulfilled? May Allah reward you with good.