Police were justified in pursuing and then patting down a man who took off running as soon as he spotted them, a federal judge held.In a written opinion last week, U.S. District Judge Edmond E. Chang denied Nicholas Williams’ motion to suppress the gun and cocaine he was carrying when he was stopped by officers.Chang rejected the argument that the officers violated the Fourth Amendment by approaching Williams in public with the purported intention of asking him about crime in the neighborhood.The officers also did not …