Fix handling of additional fields

Author: mpv1989

ChangeLog.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 
 ## [Unreleased]
 
+### Fixed
+
+- fixed handling of additional fields
+
 ## [1.4.0] - 2018-09-18
 
 ### Added

src/main/java/com/arangodb/velocypack/VPack.java

@@ -823,7 +823,6 @@ private void serializeObject(
 			builder.add(name, ValueType.OBJECT);
 			serializeFields(entity, builder, additionalFields);
 			if (!additionalFields.isEmpty()) {
-				// additionalFields.clear();
 				builder.close(true);
 			} else {
 				builder.close(false);
@@ -961,7 +960,6 @@ private void serializeMap(
 							builder, null, Collections.<String, Object> emptyMap());
 					}
 				}
-				additionalFields.clear();
 				builder.close();
 			} else {
 				builder.add(name, ValueType.ARRAY);