Is it permissible to spend money designated for charity, when there is no one to give it to, and the owner of the money is currently in need of it?

There is no harm in retracting the intention to give charity, because it does not become binding merely by intention. If someone intends to give charity and then decides not to, it is commendable for him to proceed with it, but it is not obligatory. Spending in good causes is an act of worship with great reward, and encouragement for it has been mentioned in the Qur'an and Sunnah, such as His (Allah's) saying: "And spend from that in which He has made you successors," and His saying: "And whatever you spend of good - it will be fully repaid to you, and you will not be wronged." Allah has promised replacement for those who spend, as He said: "And whatever thing you spend [in His cause] - He will compensate it; and He is the best of providers." It is also mentioned in the noble Hadith that angels supplicate for replacement for the one who spends, and for ruin for the one who withholds, and that charity from lawful earnings grows with Allah until it becomes like a mountain.