It wasn't Harry. First of all, he's been as distracted as Draco. Second, if he were going to curse you he wouldn't do something that would make you run around pestering people like Bellatrix Lestrange. He'd think that was a bad idea but also his own life sometimes gets harder when the important adults are in a bad mood, you know?

Besides, he could care less that Padma got her hair hexed off. I think he thought it was funny.