A record number of Hong Kong firms shut up shop last year as China, the mainstay of the city’s economy, trundled to its slowest economic growth in a quarter of a century and spending by mainland visitors dried up. Some 122,479 companies were dissolved, according to data from the city’s Companies Registry compiled by financial research platform Webb-site.com. New firms incorporated in Hong Kong also slid 17 percent, leaving the net number of new firms at a low since 2003’s SARS outbreak slammed the city’s economy.