Update web-sites-dotnet-deploy-aspnet-mvc-app-membership-oauth-sql-database.md

When the user has not filled out their first and last name, they will get a NullReferenceException in Microsoft.Owin.Security.AuthenticationManagerExtensions.GetExternalLoginInfo when trying to log in.
resolving merge conflict to accept pull request #1748
Merge pull request #1854 from tysonn/6-2-14c

Pulling in martijn's commit to resolve merge conflict