GAM: serialize null values

Author: mrodbratschi

gamutils/src/main/java/com/genexus/gam/utils/Dictionary.java

@@ -21,7 +21,7 @@ public class Dictionary {
 
 	public Dictionary() {
 		this.userMap = new LinkedHashMap<>();
-		this.gson = new GsonBuilder()
+		this.gson = new GsonBuilder().serializeNulls()
 			.addSerializationExclusionStrategy(new ExclusionStrategy() {
 				@Override
 				public boolean shouldSkipField(FieldAttributes f) {