Grunt error

[8beret]

After type command grunt I have such error:

D:\intro-to-protractor>grunt Loading "grunt-karma.js" tasks...ERROR

TypeError: Cannot read property 'prototype' of undefined

Running "jshint:all" (jshint) task Warning: Path must be a string. Received null Used --force, continuing.

Running "csslint:all" (csslint) task

3 files lint free.

Running "concurrent:default" (concurrent) task Loading "grunt-karma.js" tasks...ERROR

TypeError: Cannot read property 'prototype' of undefined Loading "grunt-karma.js" tasks...ERROR TypeError: Cannot read property 'prototype' of undefined

Running "watch" task Waiting...

Running "nodemon:dev" (nodemon) task [nodemon] v1.0.20 [nodemon] to restart at any time, enter rs [nodemon] watching: app/views//. gruntfile.js server.js config//.js app/**/.js [nodemon] starting node --debug server.js (node:26948) [DEP0062] DeprecationWarning: node --debug and node --debug-brk are invalid. Please use node --inspect or node --inspect-brk instead. [nodemon] app crashed - waiting for file changes before starting...