NEW YORK -- An early morning pipe-bomb explosion blew out the windows of an unoccupied van parked outside a theater owned by a former star of TV's "The Sopranos,'' police said Tuesday.The New York Police Department said it did not know whether the incident had any connection to the actor, Michael Imperioli, who owns Studio Dante. Imperioli played Christopher Moltisanti, Tony Soprano's nephew, on the popular HBO television show.His representative did not immediately return calls for comment on Tuesday.NYPD spokesman Paul Browne said there had been "no known threats to the location or its owners'' before the 1 a.m. incident....