A Hong Kong student accused of possessing a firearm without a licence was charged on Thursday with an additional offence under the national security law.Lui Sai-yu, a 24-year-old engineering student at Polytechnic University, appeared at West Kowloon Court over allegations he had been in possession of a pepper ball launcher, extendable baton and two knives for unlawful purposes.He was further accused on Thursday of inciting others to commit secession between June 30 and September 24 last year,….