Good Morning America’s main anchors have been MIA — and sources say it’s making the program risk its paper-thin lead over the Today show, RadarOnline.com has learned. Familiar faces including George Stephanopoulos and Robin Roberts were said to be no-shows during parts of June. Sources said the absentee anchors were leaving ABC in the lurch and in danger of losing precious advertising dollars. “Good Morning America has been the top-rated morning news program since 2012, but they are now holding on to that lead over Today by the skin of their teeth,” an insider spilled. Stephanopolous and Rober…