If Entity Framework (version below 5.1) on your attempt to Update-Database gives you error of “Object reference not set”, change the default start-up project to MVC project, not anything else. And try the same thing again.
This reported to be fixed in the latest 5.x version of EF, but it is a little annoyance just now.

p.s. This can be eased with parameter: -StartupProject “helloMVC” when running Update-Database command