The art world is mourning artist Jack Whitten (left) and curator Kynaston McShine.   THE WORLD OF ART lost two important figures in January—inventive abstract painter Jack Whitten (1939-2018) and pioneering MoMA curator Kynaston McShine (1935-2018). In “Jack Whitten: Five Decades of Painting,” the catalog published to coincide with Whitten’s career-spanning survey (2014-15), the artist...