title: Breeze is excluding entities with foreign key of null when they are expanded
body: <p>I have an entity in my database that has a <code>null</code> foreign key.</p>
  
  <p>When I <code>expand</code> via JavaScript or <code>Include</code> in EF the rows that have that foreign key are lost.</p>
  
  <p>Sql:</p>
  
  <pre><code>CREATE TABLE Entity
  (
      Id BIGINT NOT NULL PRIMARY KEY
  );
  
  CREATE TABLE EntityType
  (
      Id BIGINT IDENTITY NOT NULL PRIMARY KEY,
      EntityId BIGINT NULL REFERENCES Entity(Id)
  );
  
  INSERT INTO Entity(Id) VALUES (0);
  INSERT INTO Entity(Id) VALUES (1);
  
  INSERT INTO EntityType(EntityId) VALUES (0);
  INSERT INTO EntityType(EntityId) VALUES (1);
  INSERT INTO EntityType(EntityId) VALUES (NULL);
  </code></pre>
  
  <p>C#:</p>
  
  <pre><code>public class Entity
  {
      public long Id { get; set; }
  }
  
  public class EntityType
  {
      public long Id { get; set; }
      public long EntityId { get; set; }
      public Entity Entity { get; set; }
  }
  
  public class EntityMap : EntityTypeConfiguration&lt;Entity&gt;
  {
      public EntityMap()
      {
          HasKey(t =&gt; t.Id);
      }
  }
  
  public class EntityTypeMap : EntityTypeConfiguration&lt;EntityType&gt;
  {
      public EntityTypeMap()
      {
          HasKey(t =&gt; t.Id);
  
          HasRequired(t =&gt; t.Entity)
             .WithMany()
             .HasForeignKey(t =&gt; t.EntityId);
      }
  }
  
  [BreezeController]
  public class EntityController : ApiController
  {
      private readonly EFContextProvider&lt;EntityContext&gt; _contextProvider =
          new EFContextProvider&lt;EntityContext&gt;();
  
      [HttpGet]
      public IQueryable&lt;Entity&gt; Entities()
      {
          return _contextProvider.Context.Entities;
      }
  
      [HttpGet]
      public IQueryable&lt;EntityType&gt; EntityType()
      {
          return _contextProvider.Context.EntityTypes;
      }
  }
  </code></pre>
  
  <p>JS:</p>
  
  <pre><code>angular.module('App').factory('EntityTypeService', function(serviceBase) {
      function getAll {
          return serviceBase.manager.executeQuery(
              serviceBase.query.
                  from('EntityTypes').
                  expand('Entity')
          ).to$q();
      }
  
      return {
          getAll: getAll
      };
  });
  
  angular.module('App').controller('HomeCtrl', function($scope, EntityTypeService) {
      EntityTypeService.getAll().then(function(data) {
          $scope.entityTypes = data.results;
      });
  });
  </code></pre>
  
  <p>When I examine <code>$scope.entityTypes</code> there is only rows with the <code>EntityId</code> that is not <code>null</code>.</p>