Sarah Cunningham, a British painter whose abstracted pictures of forests charmed audiences on both sides of the Atlantic, has died after having gone missing in London this past weekend. She was 31, according to the Camden Police. Lisson Gallery, which represents Cunningham, had posted news of her disappearance on Sunday, saying that she was last seen on Saturday. On Monday, the Camden Police said it had been informed of what it described as “a casualty on the tracks” of the London Underground. At the time, the body had not been formally identified by Cunningham’s family, which had been notified of...