samples: updated legacy field in detectintentknoledge (#569)

Author: b-loved-dreamer

dialogflow/snippets/src/main/java/com/example/dialogflow/DetectIntentKnowledge.java

@@ -80,7 +80,11 @@ public static Map<String, KnowledgeAnswers> detectIntentKnowledge(
         System.out.format(
             "Detected Intent: %s (confidence: %f)\n",
             queryResult.getIntent().getDisplayName(), queryResult.getIntentDetectionConfidence());
-        System.out.format("Fulfillment Text: '%s'\n", queryResult.getFulfillmentText());
+        System.out.format(
+            "Fulfillment Text: '%s'\n",
+            queryResult.getFulfillmentMessagesCount() > 0
+                ? queryResult.getFulfillmentMessages(0).getText()
+                : "Triggered Default Fallback Intent");
         KnowledgeAnswers knowledgeAnswers = queryResult.getKnowledgeAnswers();
         for (Answer answer : knowledgeAnswers.getAnswersList()) {
           System.out.format(" - Answer: '%s'\n", answer.getAnswer());