Fix "NoneType" error on user delete
Fix "NoneType" error on user delete

We used to have the following error: "'NoneType' object has no attribute
'id'". This was caused by the fact that we were trying to delete
UserSocialAuth objects created for backend PEAMOpenIdConnect.

StartupsPoleEmploi/labonneboite,StartupsPoleEmploi/labonneboite,StartupsPoleEmploi/labonneboite,StartupsPoleEmploi/labonneboite