When a collection is empty, render returns nil.

railties/guides/source/layouts_and_rendering.textile

@@ -1093,6 +1093,13 @@ In Rails 3.0, there is also a shorthand for this. Assuming +@products+ is a coll
 
 Rails determines the name of the partial to use by looking at the model name in the collection. In fact, you can even create a heterogeneous collection and render it this way, and Rails will choose the proper partial for each member of the collection:
 
+In the event that the collection is empty, +render+ will return nil, so it should be fairly simple to provide alternative content.
+
+<erb>
+<h1>Products</h1>
+<%= render(@products) || 'There are no products available.' %>
+</erb>
+
 * +index.html.erb+
 
 <erb>