Closed Issue: Stored Procs :: NullReferenceException when trying to scaffold migration for entity with Enum Key that is mapped to stored procedures [1277]

Create the following model:

```
namespace StoredProcsCustomize
{
public enum MilitaryRank
{
Private,
Major,
Colonel,
General,
};

public class EnumKey
{
public MilitaryRank Id { get; set; }
public string Name { get; set; }
}

public class MyContext : DbContext
{
public DbSet<EnumKey> Keys { get; set; }
}
```

Enable-Migrations
Add-Migration Mig1
Update-Database

now, add the following lines to the context:


```
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<EnumKey>().MapToStoredProcedures();
}

```

Add-Migration Mig2

throws the following exception:

System.NullReferenceException: Object reference not set to an instance of an object.
at System.Data.Entity.Migrations.Infrastructure.ModificationCommandTreeGenerator.SetFakeReferenceKeyValues(Object entity, EntityType entityType)
at System.Data.Entity.Migrations.Infrastructure.ModificationCommandTreeGenerator.<Generate>d__12`1.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.<CastIterator>d__b1`1.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.GenerateFunctionBody[TCommandTree](StorageEntityTypeModificationFunctionMapping modificationFunctionMapping, Func`3 treeGenerator, Lazy`1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator, String functionName, String rowsAffectedParameterName)
at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.GenerateInsertFunctionBody(StorageEntityTypeModificationFunctionMapping modificationFunctionMapping, Lazy`1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator)
at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.<BuildCreateProcedureOperations>d__cd.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__31`3.MoveNext()
at System.Linq.Enumerable.<ConcatIterator>d__71`1.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(ModelMetadata source, ModelMetadata target, Lazy`1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator)
at System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff(XDocument sourceModel, XDocument targetModel, Lazy`1 modificationCommandTreeGenerator, MigrationSqlGenerator migrationSqlGenerator)
at System.Data.Entity.Migrations.DbMigrator.Scaffold(String migrationName, String namespace, Boolean ignoreChanges)
at System.Data.Entity.Migrations.Design.MigrationScaffolder.Scaffold(String migrationName, Boolean ignoreChanges)
at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Scaffold(MigrationScaffolder scaffolder)
at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Run()
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
at System.Data.Entity.Migrations.Design.ToolingFacade.Scaffold(String migrationName, String language, String rootNamespace, Boolean ignoreChanges)
at System.Data.Entity.Migrations.AddMigrationCommand.Execute(String name, Boolean force, Boolean ignoreChanges)
at System.Data.Entity.Migrations.AddMigrationCommand.<>c__DisplayClass2.<.ctor>b__0()
at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Comments: Verified, added functional tests, closing