Bartbot Stacktrace

TypeError: path must be absolute or specify root to res.sendFile
    at ServerResponse.sendFile (/var/www/html/bb/callback/node_modules/express/lib/response.js:425:11)
    at app.get (/var/www/html/bb/callback/api.js:254:6)
    at Layer.handle [as handle_request] (/var/www/html/bb/callback/node_modules/express/lib/router/layer.js:95:5)
    at next (/var/www/html/bb/callback/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/var/www/html/bb/callback/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/var/www/html/bb/callback/node_modules/express/lib/router/layer.js:95:5)
    at /var/www/html/bb/callback/node_modules/express/lib/router/index.js:281:22
    at Function.process_params (/var/www/html/bb/callback/node_modules/express/lib/router/index.js:335:12)
    at next (/var/www/html/bb/callback/node_modules/express/lib/router/index.js:275:10)
    at jsonParser (/var/www/html/bb/callback/node_modules/body-parser/lib/types/json.js:110:7)