Error: [/opt/app/lua/base/db.lua:58: attempt to index local 'db' (a nil value)

stack traceback:

/opt/app/lua/base/db.lua:58: in function 'query'

/opt/app/lua/base/data/data_v3.lua:110: in function 'article_with_intro'

/opt/app/lua/www_5200_new/remote_novel.lua:16: in function

[C]: in function 'xpcall'

/opt/app/lua/www_5200_new/www.lua:69: in main chunk]