Reuters/Jonathan ErnstWASHINGTON (Reuters) - The White House press corps gathered on Saturday for its annual black-tie dinner, a toned-down affair this year after Donald Trump snubbed the event, becoming the first incumbent U.S. president to bow out in 36 years. Without Trump, who scheduled a rally instead to mark his 100th day in office, the usually celebrity-filled soiree hosted by the White House Correspondents' Association took a more sober turn, even as it pulled in top journalists and Washington insiders. Most of Trump's administration also skipped the event in solidarity with the president, who has repeatedly accused the press of mistreatment.