Ember-CLI- TypeError: Cannot convert a Symbol value to a string

I am trying to compile my Cordova code for iOS but somehow when I try to run "ember serve" in /app/www/ folder then I get this error:

(node:21854) fs: re-evaluating native module sources is not supported. If you are using the graceful-fs module, please update it to a more recent version.
(node:21854) fs: re-evaluating native module sources is not supported. If you are using the graceful-fs module, please update it to a more recent version.
version: 0.1.7
Looks like you have a different program called watchman, falling back to NodeWatcher
Cannot convert a Symbol value to a string
TypeError: Cannot convert a Symbol value to a string
at RegExp.test (native)
at Symbol.hasOwnProperty (/Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/ember-cli/node_modules/es6-module-transpiler/dist/es6-module-transpiler.js:163:43)
at /Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/6to5-core/node_modules/core-js/library.js:136:17
at setToStringTag (/Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/6to5-core/node_modules/core-js/library.js:88:13)
at /Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/6to5-core/node_modules/core-js/library.js:610:3
at /Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/6to5-core/node_modules/core-js/library.js:614:2
at Object. (/Users/apple/Desktop/bob/we/source-code/code/app/www/node_modules/6to5-core/node_modules/core-js/library.js:2101:2)
at Module._compile (module.js:570:32)
at Object.Module._extensions..js (module.js:579:10)
at Module.load (module.js:487:32)

Please suggest me how to fix this.