Ember 2, Show message for an empty model instead of loading in hbs template, each or if

I use very often in my code (and I don't know if I'm right to use it):

  <div>post.title</div>



  <div>I'm loading the posts...</div>

and until today everything OK.

But now I don't know if the model.posts is empty or not.

How to show an error instead of loading forever an empty array?