Data for issue reproduction

marten-orderby-dictionaryvalue-data.cs

 var entity1 = new Car
                {
                    Id = Guid.NewGuid(),
                    Name = "car-1",
                    Attributes = new Dictionary<string, AttributeValue>{
                        {"petrol",
                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="diesel",
                        }},
                        {"manufacturer",
                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="VW"
                        }}
                    }
                };

                var entity2 = new Car
                {
                    Id = Guid.NewGuid(),
                    Name = "car-2",
                    Attributes = new Dictionary<string, AttributeValue>{
                        {"manufacturer",

                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="VW"
                        }},
                        {"petrol",
                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="petrol"
                        }
                        },
                        {"ABS",
                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="yes"
                        }
                        }
                    }
                };

                var entity3 = new Car
                {
                    Id = Guid.NewGuid(),
                    Name = "car-3",
                    Attributes = new Dictionary<string, AttributeValue>{
                        {"manufacturer",

                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="Audi"
                        }},
                        {"petrol",
                        new AttributeValue{
                            Id = Guid.NewGuid(),
                            Value="lpg"
                        }
                        }
                    }
                };