solnic/virtus — pull request #117 by indrekj (2012-10-01 15:22:12+00:00)
Title: Raise more readable error message

```
class User
include Virtus
attribute :adderss, Address
end
```

When I accidentally set a wrong attribute to the user address `User.new.address = Object.new`, then I'll get an error `undefined method `each' for nil:NilClass`. This doesn't tell much about what was wrong. I tried to make it a bit better with this pull request.