Mel Gibson injured himself on the set of “The Beaver,” which he filmed just as tapes of him berating then-girlfriend Oksana Grigorieva were made public. Director Jodie Foster tells the Hollywood Reporter the prop department “messed up” when setting up a lamp: “When he smacked his head, it just — whoosh! — blood was gushing . . . I can’t tell you how many ‘I’m so sorry’ notes I sent.” The movie premieres at South by Southwest today.