Removes unnecessary emptyRegions call in LayoutView.

Resolves #1831
Because of this right?
```js
this.layoutView = new this.LayoutViewBoundRender({
  model: new Backbone.Model()
});
this.sinon.spy(this.layoutView.regionOne, 'empty');
this.layoutView.render(); // 0 - not called at first
 
this.view = new Backbone.View();
this.view.destroy = function() {};
this.layoutView.regionOne.show(this.view); // 1

this.layoutView.render(); // 2
this.layoutView.regionOne.show(this.view); // 3
this.region = this.layoutView.regionOne;
```