[ASTERIXDB-2510][OTH] Fix Forward Operator JSON Plan

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Add separator in forward operator name and expression
  JSON fields.

Change-Id: Ibbffeebe82fff8e5282ca3c16343f9c909d35262
Reviewed-on: https://asterix-gerrit.ics.uci.edu/3117
Reviewed-by: Ali Alsuliman <ali.al.solaiman@gmail.com>
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
index 8ba2aff..f502d14 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
@@ -633,6 +633,7 @@
     @Override
     public Void visitForwardOperator(ForwardOperator op, Integer indent) throws AlgebricksException {
         addIndent(indent).append("\"operator\": \"forward\"");
+        addIndent(0).append(",\n");
         addIndent(indent).append("\"expressions\": \""
                 + op.getRangeMapExpression().getValue().accept(exprVisitor, indent).replace('"', ' ') + "\"");
         return null;