Call profile fields controller with correct args

My intension:
I wanted to make the profile fields on the user page persisted.
The fields 
* About
* Study
* Organization
* Bank account

My changes:
1. In the HAML, the profile fields controller is called with the profileable type.
2. In the controller, if the profileable type is missing, an exception is raised.

The effect:
The changes in the fields are still visible after a reload of the user page.