A woman who snuck a gun into her holding cell at Newark Police Headquarters and then tried to hide it there was convicted Thursday, authorities said. Talisha Arrington, 34, of Newark was found guilty of second-degree unlawful possession of a handgun and fourth-degree tampering with evidence, the Essex County Prosecutor’s Office said in a release. Arrington was arrested on July 15, 2020 after a confrontation with another customer at a White Castle on Elizabeth Avenue in Newark and was detained in the holding cell at the police station on Clinton Avenue, the office said. The nature of the incide…