In a departure from the string of polished pop hits that made Ed Sheeran one of the world’s bestselling music artists, his new album, “Subtract,” is a stripped-down return to his singer-songwriter roots. The unassuming superstar talks with correspondent Seth Doane about how his latest music is very much a reflection of recent times, filled with personal challenges, loss, mental health struggles, and controversy. He also discusses the recent lawsuit accusing him of plagiarism (which a jury this past week rejected).