Description
Unable to log in through the use of another provider than ezplatform (when used UserWrapped class)

Steps to reproduce
1. Configure in_memory provider
2. Add provider in_memory to firewalls ezpublish_front
3. Go to Admin login page
4.  Try to login

In eZ Platform 2.5 in_memory provider work correctly

Actual result:
A blank site with information about the empty response (Chrome) or blank page

Expected results

A successful login to the platform