Do not try to load belongs_to associations with null key
Do not try to load belongs_to associations with null key

For a belongs_to association where the foreign key is nil, the existing
code would create a scope on the assoicated table with a where clause
selecting id IS NULL. This would always fail to find any records, but
it's better to not perform the query at all.

ActsAsParanoid/acts_as_paranoid