dance?

So my friend bought 2 tickets to the dance and he was going to go with a girl but then she changed her mind and is going with someone else. So he's stuck with 2 tickets and he wants to go to the dance but he doesn't want to go by himself. I would love to go with him but I don't think he would want to go with me because I'm his ex but we are still really close friends. It kinda seems like he's depressed about it. I can tell he wanted to go but now he can't. And it makes me upset to see him like this. Should I ask him if he would like to go with me? If so how would I ask? I just have this feeling if I do ask he would say no. But I really want him to go because I know he wants to go.