WASHINGTON — For all the concern over leaks at the White House, a more pressing problem might be the sinkhole on the North Lawn that appears to be growing by the day.The pit in the ground, which was first reported by White House correspondents on site this week, appears to have opened just outside the press briefing room and deputy White House press secretary Hogan Gidley’s office.Steve Herman, a reporter with Voice of America, tweeted that he first spotted the sinkhole last week.