Sandy Gallin, whose long career as an agent, talent manager and producer included clients from Barbra Streisand, Nicole Kidman and Richard Pryor to Michael Jackson, Cher and Joni Mitchell, has died. He was 76. His death was announced by friend Bruce Bozzi on Instagram today. “We lost a shining light this morning,” wrote Bozzi (see the post below). Gallin began his career work in the mailroom of the GAC talent agency, according to a bio on his official website, becoming an…