Fix a Node JS app

We have a small node js app, which is a mqtt broker plus a basic GUI for managing some settings.

We have one error:

TypeError: expecting an array or an iterable object but got [object Null]
at apiRejection (/var/www/sites/gzih/node_modules/bluebird/js/release/promise.js:10:27)
at PromiseArray.init [as _init] (/var/www/sites/gzih/node_modules/bluebird/js/release/promise_array.js:64:19)
at Promise._settlePromise (/var/www/sites/gzih/node_modules/bluebird/js/release/promise.js:601:21)
at Promise._settlePromise0 (/var/www/sites/gzih/node_modules/bluebird/js/release/promise.js:649:10)
at Promise._settlePromises (/var/www/sites/gzih/node_modules/bluebird/js/release/promise.js:729:18)
at _drainQueueStep (/var/www/sites/gzih/node_modules/bluebird/js/release/async.js:93:12)
at _drainQueue (/var/www/sites/gzih/node_modules/bluebird/js/release/async.js:86:9)
at Async._drainQueues (/var/www/sites/gzih/node_modules/bluebird/js/release/async.js:102:5)
at Immediate.Async.drainQueues [as _onImmediate] (/var/www/sites/gzih/node_modules/bluebird/js/release/async.js:15:14)
at processImmediate (internal/timers.js:458:21)

We need some help to fix this error.

Please contact us if you have experience with node js and MQTT.