"Charlie's in Romania studying dragons, and Bill's in Africa doing something for Gringotts[bank]," said Ron. "Did you hear about Gringotts? It's been all over the Daily Prophet, but I don't suppose you get that with the Muggles - someone tried to rob a high security vault."
"Really? What happened to them?"
"Nothing, that's why it's such big news. They haven't been caught. My dad says it must've been a powerful Dark wizard to get round Gringotts, but they don't think they took anything, that's what's odd. 'Course, everyone gets scared when something like this happens in case You-Know-Who's behind it."
(Harry Potter and the Sorcerer's Stone)
Does highlighted 'it' indicate ‘someone’ who wasn’t known its sex; or is it an anticipatory it (dummy it) for ‘a powerful Dark wizard to get round Gringotts’?