fix: Fixed NullReferenceException when writing null strings to CSV

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Changed
  - Performance improvements when working with xml attributes
+ - Fixed NullReferenceException when writing null strings to CSV
 
 ### Removed
  - Removed IcdXmlAttribute

ICD.Common.Utils/Csv/CsvWriter.cs

@@ -79,6 +79,8 @@ namespace ICD.Common.Utils.Csv
 		[PublicAPI]
 		public void AppendValue(string value)
 		{
+			value = value ?? string.Empty;
+
 			if (!m_NewLine)
 				m_Writer.WrappedTextWriter.Write(m_Seperator);