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:182: in function 'sortArticleOrderBy'

/opt/app/lua/www_5200_new/sort.lua:19: in function 'buildSort'

/opt/app/lua/www_5200_new/sort.lua:64: in function

[C]: in function 'xpcall'

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