rest.cpp: change HTTP_INTERNAL_SERVER_ERROR to HTTP_BAD_REQUEST

doc/release-notes.md

@@ -59,6 +59,10 @@ git merge commit are mentioned.
 
 ### RPC and REST
 
+UTXO set query (`GET /rest/getutxos/<checkmempool>/<txid>-<n>/<txid>-<n>/.../<txid>-<n>.<bin|hex|json>`) responses
+were changed to return status code HTTP_BAD_REQUEST (400) instead of HTTP_INTERNAL_SERVER_ERROR (500) when requests
+contain invalid parameters.
+
 ### Configuration and command-line options
 
 ### Block and transaction handling