activeadmin/activeadmin — pull request #3490 by bolshakov (2014-10-15 10:01:59+00:00)
Title: Feature/attributes table for nil

If you pass `nil` to `attributes_table_for` it raises exception. So app have a lot of boilerplate code:

```ruby
if user.profile.present?
attributes_table_for user.profile
else
span class: 'empty' do
'Empty'
end
end
```

This PR implements such behavior for `attributes_table_for`. So it render Empty tag if `nil` given as attribute