Hi,

I am using the plugin, with either Site.CreateFacebookUsers and Site.OneToOneEmailMapping set to True.
On first-time login with a new facebook account an foreign key exception is thrown from the CreateOrUpdateUserFacebook action in LoginFacebookUser. 

In my opinion there is an assignment missing when User account is created/updated to prevent the LocalUserFacebook.id to be Null. Adding the assignment fixed the issue for me, anyway.