changelog update

Author: rashtao

ChangeLog.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 ## [6.16.1] - 2022-02-23
 
 - fixed retry behavior of HTTP connections in case of timeout exceptions (#429)
+- fixed NPE when serializing ArangoSearch properties (#427)
 
 ## [6.16.0] - 2022-01-27