Edited Unassigned: Should get null instead of "NULL" for varchar DEFAULT NULL [156]

SQL
---
```SQL

CREATE TABLE [dbo].[CC] (
[Id] int NOT NULL IDENTITY(1,1) ,
[Desc] varchar(MAX) NULL DEFAULT NULL ,
[X1] varchar(255) NULL
)


GO

-- ----------------------------
-- Indexes structure for table CC
-- ----------------------------

-- ----------------------------
-- Primary Key structure for table CC
-- ----------------------------
ALTER TABLE [dbo].[CC] ADD PRIMARY KEY ([Id])
GO
```
but got
```C#

// CC
public class Cc
{
public int Id { get; set; } // Id (Primary key)
public string Desc { get; set; } // Desc
public string X1 { get; set; } // X1

public Cc()
{
Desc = "NULL";
}
}
```
instead of `Desc = null;`

Tested in MSSQL & POCO 2.16.0/1