ReferenceError: err is not defined

[Nas-au]

ReferenceError: err is not defined
at Strategy._verify (/Users/nas/Desktop/bot_web/index.js:25:5)
at /Users/../Desktop/bot_web/node_modules/passport-oauth2/lib/strategy.js:193:24
at /Users/../Desktop/bot_web/node_modules/passport-discord/lib/strategy.js:87:24
at /Users/../Desktop/bot_web/node_modules/passport-discord/lib/strategy.js:103:13
at passBackControl (/Users/../Desktop/bot_web/node_modules/oauth/lib/oauth2.js:134:9)
at IncomingMessage. (/Users/../Desktop/bot_web/node_modules/oauth/lib/oauth2.js:157:7)
at IncomingMessage.emit (events.js:165:20)
at endReadableNT (_stream_readable.js:1101:12)
at process._tickCallback (internal/process/next_tick.js:152:19)

[zignis]

Kindly provide the relevant snippet/code.