Don't try to get the subclass if the inheritance column doesn't exist

The `subclass_from_attrs` method is called even if the column specified by
the `inheritance_column` setting doesn't exist. This prevents setting associations
via the attributes hash if the association name clashes with the value of the setting,
typically `:type`. This worked previously in Rails 3.2.

1 files changed, 5 insertions, 0 deletions

diff --git a/activerecord/test/models/shop.rb b/activerecord/test/models/shop.rb
index 81414227ea..607a0a5b41 100644
--- a/activerecord/test/models/shop.rb
+++ b/activerecord/test/models/shop.rb
@@ -5,6 +5,11 @@ module Shop
 
   class Product < ActiveRecord::Base
     has_many :variants, :dependent => :delete_all
+    belongs_to :type
+
+    class Type < ActiveRecord::Base
+      has_many :products
+    end
   end
 
   class Variant < ActiveRecord::Base