No wonder he doesn’t think there’s a problem. The police have been laboring to keep Mayor de Blasio in a bum-free bubble — clearing nuisance-causing vagrants from his view at Gracie Mansion and as he travels in the city. On Wednesday, two hours before de Blasio was due to walk through Washington Square Park, cops arrived en masse to clear out the quality-of-life-ruining bums who drink from paper bags, sprawl on benches and pee in public. “They had to clear all the homeless out before he got there,” for a Ramadan fast-breaking dinner at the NYU Islamic Center, said one...