Calling isEmpty on instances of ObjectProxy wrapping ArrayProxy throws Assertion Failed: You attempted to access the length property

[janvotava]

While working on one of our projects, I encountered an error which I managed to boil down to the following:

Ember.isEmpty(Ember.ObjectProxy.create({
  content: Ember.ArrayProxy.create({
    content: Ember.A([])
  })
}))

Looks like a regression caused by utilisation of ES5 getters, it worked in Ember 3.0.0.

It breaks for example ember-changeset with ember-data-model-fragments.