I believe it would be wrong, in normal circumstances, to break a promise made to someone who died meanwhile, even if no one will benefit from the keeping of the promise. I also believe that, if keeping the promise would cause great damage to someone (to the promisor or to somebody else), it would be right not to keep it (it could even be wrong to keep it). Now, where should we draw the line between the two kinds of circumstances? If the promisee were alive, we could compare his damage to the damage of somebody else, but, since he/she is dead, to what should we compare the damage caused by keeping the promise?