Substitute .sort_by for .order

[alxcrrll]

.sort_by is a Ruby method from Enumerable that is used to sort arrays (or array like objects). Using .sort_by will cause all the records to be loaded from the database into the servers memory, which can lead to serious performance problems (as well as your issue with nil values).

.order is a ActiveRecord method that adds a ORDER BY clause to the SQL select statement. The database will handle sorting the records. This is preferable in 99% of cases.