PaulUithol/Backbone-relational — pull request #105 by DouweM (2012-04-16 15:28:05+00:00)
Title: Serialize `null` relations as `null` in #toJSON().

Relations with a value of `null` used to not be included in the object returned by `#toJSON()` at all, but are now properly represented as `null`.

This is useful when you want to get rid of a relation between two objects by setting the relation to `null`, and you want this value to actually be saved to the server.