ABC bigwigs are going potty to find the identity of the leaker behind the Amy Robach tape — after the alleged source posted a letter online slamming the network under the name “Ignotus,” a wizard from the “Harry Potter” franchise. After junior producer Ashley Bianco denied leaking the tape, on which the anchor complained ABC News killed her interview with Jeffrey Epstein victim Virginia Roberts Giuffre, someone purporting to be the actual leaker and still working at the network posted a letter on Project Veritas blasting ABC’s “mission of seek and destroy” to conjure up the mysterious mole. Project Veritas...