Fix request collection count request on XEP-0059

Monitoring Plugin request of collection count according 2.7 of XEP-0059
More information on https://community.igniterealtime.org/message/250310

src/plugins/monitoring/src/java/com/reucon/openfire/plugin/archive/xep0136/IQRetrieveHandler.java

@@ -76,12 +76,14 @@ public class IQRetrieveHandler extends AbstractIQHandler {
 			addMessageElement(chatElement, conversation, message);
 		}
 
-		if (resultSet != null && messages.size() > 0) {
-			resultSet.setFirst((long) fromIndex);
-			resultSet.setFirstIndex(fromIndex);
-			resultSet.setLast((long) toIndex - 1);
-			resultSet.setCount(conversation.getMessages().size());
-			chatElement.add(resultSet.createResultElement());
+		if (resultSet != null) {
+			if (messages.size() > 0) {
+                		resultSet.setFirst((long) fromIndex);
+                		resultSet.setFirstIndex(fromIndex);
+                		resultSet.setLast((long) toIndex - 1);
+            		}
+            		resultSet.setCount(conversation.getMessages().size());
+            		chatElement.add(resultSet.createResultElement());
 		}
 
 		return reply;