THIS IS A CRACK-UP: Vegas prosecutor David Schubert (at left in the photo above), who took Bruno Mars and Paris Hilton to task for cocaine possession, was busted Saturday on charges of buying crack from a street dealer near the strip. Schubert was pulled over around 5 p.m. and swallowed a crack rock as an undercover cop closed in, Clark County DA David Roger told the N.Y. Daily News. A second rock was recovered from his car, Roger said. The street dealer arrested at the scene later told cops Schubert was a regular customer who started buying six or seven months ago and used him to score three to four times a week, a police report obtained by TMZ.com said. (3/22a)