fix ember 1.10 error
fix ember 1.10 error

funkensturm/ember-cli-file-picker,imanhodjaev/ember-cli-file-picker,ryanlabouve/ember-cli-file-picker,funkensturm/ember-cli-file-picker,ryanlabouve/ember-cli-file-picker,imanhodjaev/ember-cli-file-picker