Correcly compute list-container height when emptyView is removed

Hi,

I'm using **Ember.ListView** with **Ember.ReusableListItemView** and I noticed that while using a valid **emptyView** (extended from **Ember.View**) the height of the list-container is not correctly computed when the **emptyView** is removed and the **ReusableListItemView**s are created.

Also I noticed that every time the **content** array was changed the **removeEmptyView** funcion was called regardless if the **emptyView** was actually displayed, doing not useful additional calls in case the list-view is used to display changing data.

Let me know if u have any comments/questions