[BUGFIX beta] proxy meta on PromiseArray

[pangratz]

This closes #5129.

I am unsure if this is the correct way to fix this or if something else is fishy...

Maybe it's because of this 🤔:

data/addon/-private/system/record-arrays/adapter-populated-record-array.js

Lines 51 to 52 in 5fceead

	// yes we are touching `this` before super, but ArrayProxy has a bug that requires this.
	this.set('content', this.get('content') || Ember.A());

[bmac]

Thanks @pangratz.