TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
   at assertPath (path.js:39:11)
   at Object.join (path.js:1152:7)
   at fileStorage.findOne (/home/ubuntu/node_modules/contentstack-express/lib/utils/db/providers/FileSystem.js:119:51)
   at /home/ubuntu/node_modules/contentstack-express/lib/utils/db/helper.js:442:25
   at bound (domain.js:395:14)
   at runBound (domain.js:408:12)
   at tryCatcher (/home/ubuntu/node_modules/bluebird/js/release/util.js:16:23)
   at Promise._settlePromiseFromHandler (/home/ubuntu/node_modules/bluebird/js/release/promise.js:512:31)
   at Promise._settlePromise (/home/ubuntu/node_modules/bluebird/js/release/promise.js:569:18)
   at Promise._settlePromiseCtx (/home/ubuntu/node_modules/bluebird/js/release/promise.js:606:10)
   at _drainQueueStep (/home/ubuntu/node_modules/bluebird/js/release/async.js:142:12)
   at _drainQueue (/home/ubuntu/node_modules/bluebird/js/release/async.js:131:9)
   at Async._drainQueues (/home/ubuntu/node_modules/bluebird/js/release/async.js:147:5)
   at Immediate.Async.drainQueues (/home/ubuntu/node_modules/bluebird/js/release/async.js:17:14)
   at runCallback (timers.js:705:18)
   at tryOnImmediate (timers.js:676:5)