source code file Store.cs
 private void MakeUpdates(IDataSource ds, XmlDocument xml)
{
     ......
                record = node;
                values = new SortedList(this.Reader.Reader.Fields.Count);
                keys = new SortedList();
                oldValues = new SortedList();

                foreach (RecordField field in this.Reader.Reader.Fields)
                {
                    XmlNode keyNode = node.SelectSingleNode(field.Name);
                    //modified
                    //values[field.Name] = keyNode != null ? keyNode.InnerText : null;
                    values[field.Name] = (keyNode != null && !string.IsNullOrEmpty(keyNode.InnerText)) ? keyNode.InnerText : null;
                    
                   
                }
}
source code file StoreDataHandler.cs
        [Description("")]
        public XmlDocument XmlData
        {
            get
            {
                if (xmlData == null)
                {
                    RecordsToXmlConverter converter = new RecordsToXmlConverter();
                    //modified
                    //xmlData = (XmlDocument)JsonConvert.DeserializeObject(JsonData, typeof(XmlDocument), converter);
                    XmlDocument doc=  (XmlDocument)JsonConvert.DeserializeObject(JsonData, typeof(XmlDocument), converter);
                    xmlData = new XmlDocument();
                    xmlData.LoadXml(doc.InnerXml);
                }

                return xmlData;
            }
        }