Make collection and collection_from_object methods return an array

This transforms for instance scoped objects into arrays and avoid
unneeded queries

[#5958 state:committed]

actionpack/lib/action_view/render/partials.rb

@@ -339,13 +339,14 @@ def render_partial(object = @object)
 
       def collection
         if @options.key?(:collection)
-          @options[:collection] || []
+          collection = @options[:collection]
+          collection.respond_to?(:to_ary) ? collection.to_ary : []
         end
       end
 
       def collection_from_object
         if @object.respond_to?(:to_ary)
-          @object
+          @object.to_ary
         end
       end