将UserId分配给外键= null

I'm using Entity Framework 5 and MVC 4, with .NET 4.5 using Code First migrations. I have foreign keys between two entities in a 1 to zero-or-1 relationship. When I try to create the record for Jogger everything blows up. I get error messages that are either:I'm using Entity Framework 5 and MVC 4, with .N