Update yggdrasil.js to fix bug


![popucf9](https://cloud.githubusercontent.com/assets/3320430/5154244/314f9da8-728b-11e4-8d38-d934ad6a5017.png)

This fixes a crash that occurs on line 310 of index.js where it tries to read the value of client.session.selectedProfile.id which doesn't exist if the session was acquired by a refresh with old auth details.