The Registration Form return error "ArgumentNullException: Value cannot be null." in new MVC 6 project

I just have created a new simple MVC 6 project (with Entity Framework 7), I added the connection string to database in project.json

Then I made migration to create user tables in database.

After run application, And when go to do register new user, I receive below error after fill registration form and click on Register button:

An unhandled exception occurred while processing the request.

ArgumentNullException: Value cannot be null.
Parameter name: entityType
Microsoft.Data.Entity.Utilities.Check.NotNull[T](T value, String parameterName)

Any One can help? Any idea to know more about this error?