The authorship of The Associated Press’s renowned “napalm girl” photograph is being called into question in the new documentary “The Stringer,” which premiered at the Sundance Film Festival in Utah. A freelance Vietnamese photographer named Nguyen Thanh Nghe claims that he took the iconic photo of Kim Phuc on June 8, 1972, not retired AP photographer Nick Ut. Ut has long been credited for the image. Representatives for the AP, who saw the film for the first time at the premiere, are contesting the implication that the company reviewed their findings and dismissed them…