ryanb/cancan — pull request #966 by knoopx (2013-11-21 13:22:14+00:00)
Title: FIX: Variable collision prevents defining permissions with multiple nested conditons. closes #965

Example
```ruby
can :read, Comment, post: {private: false, author_id: author.id}
```
Raises `NoMethodError: undefined method table_name for nil:NilClass`