don't refetch conversation parts if list is empty

Author: mmartinic

intercom-java/src/main/java/io/intercom/api/Conversation.java

@@ -265,8 +265,8 @@ public long getUpdatedAt() {
     }
 
     public ConversationPartCollection getConversationPartCollection() {
-        if (conversationPartCollection == null || conversationPartCollection.getPage().isEmpty()) {
-            this.conversationPartCollection = find(this.getId()).getConversationPartCollection();
+        if (conversationPartCollection == null) {
+            conversationPartCollection = find(this.getId()).getConversationPartCollection();
         }
 
         return conversationPartCollection;