Late on Saturday night, as Mavericks fans reveled in Deep Ellum, sipped cocktails in East Dallas, or downed Modelos in Oak Cliff, the NBA team sent its fans spiraling into basketball despair when it traded Slovenian wunderkind Luka Dončić to the Los Angeles Lakers for a package of players centered on 31-year-old All-Star center Anthony Davis.Before sunrise, a small group of obsessive fans gathered outside the American Airlines Center, some holding signs that called for the Mavericks to fire Nico Harrison, the team’s general manager. The ground in front of the statue of Dirk Nowitzki was defaced with the words “F— Nico you bum.” The following afternoon, another, larger group returned to the arena and chanted “F— Nico Harrison” as passing cars honked in agreement.…