Longtime Nickelodeon personality Marc Summers stormed off set after allegedly being “ambushed” during an interview for the explosive new docuseries that exposed child sex abuse and a toxic workplace at the kids’ television channel, RadarOnline.com has learned. In a teaser for an upcoming episode of Elvis Duran and the Morning Show, Summers said that when he agreed to participate in the documentary, Quiet on Set: The Dark Side of Kids TV, he was unaware of its subject matter. The legendary Nick host said the Investigation Discovery filmmakers pulled a “bait and switch” when he showed up to appe…