Added test for case without object_changes column

test/test_helper.rb

@@ -47,3 +47,11 @@ def change_schema
   end
   ActiveRecord::Migration.verbose = true
 end
+
+def remove_object_changes_column
+  ActiveRecord::Migration.verbose = false
+  ActiveRecord::Schema.define do
+    remove_column :versions, :object_changes
+  end
+  ActiveRecord::Migration.verbose = true
+end

test/unit/model_test.rb

@@ -102,6 +102,12 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
           assert_equal ({'name' => ['Henry', 'Harry']}), @widget.versions.last.changeset
         end
 
+        should 'return nil after call changeset method if object_changes column doesn\'t exist' do
+          remove_object_changes_column
+          Version.reset_column_information
+          assert_nil @widget.versions.last.changeset
+        end
+
         if defined?(ActiveRecord::IdentityMap) && ActiveRecord::IdentityMap.respond_to?(:without)
           should 'not clobber the IdentityMap when reifying' do
             module ActiveRecord::IdentityMap