To expand on that, we're checking to see if the attribute has any values or not, presuming if it is empty it will be nil. and it will return true here. However an empty array with #nil? returns false and we're suggesting forcing this into an array above, so use #empty?
```
1.9.3p125 :001 > [].nil?
 => false 
1.9.3p125 :002 > [].empty?
 => true 
```