Producers of Broadway’s “Rock of Ages” were not amused to be brought into the mess that occurred when an audience member vomited over the balcony at Paul Rudd’s play “Grace.” A rep for Rudd’s show had told us of the theatergoer who heaved over a mezzanine railing at the Cort Theatre on Wednesday onto a dozen audience members sitting below, “We suspect that the audience member in question meant to see ‘Rock of Ages’ and stumbled into the wrong theater.” A “Rock” rep responded, “Rock of Ages resents the implication that our patrons can’t handle their alcohol with ‘grace.’ Unlike what goes on at the Cort Theatre, clearly, what happens at ‘Rock of Ages’ stays at ‘Rock of Ages.’ ”