ATLAS-3400: Add null-check on kafkaConsumer object in AtlasKafkaConsumer when polling new messages

notification/src/main/java/org/apache/atlas/kafka/AtlasKafkaConsumer.java

@@ -66,7 +66,7 @@ public class AtlasKafkaConsumer<T> extends AbstractNotificationConsumer<T> {
 
         List<AtlasKafkaMessage<T>> messages = new ArrayList();
 
-        ConsumerRecords<?, ?> records = kafkaConsumer.poll(timeoutMilliSeconds);
+        ConsumerRecords<?, ?> records = kafkaConsumer != null ? kafkaConsumer.poll(timeoutMilliSeconds) : null;
 
         if (records != null) {
             for (ConsumerRecord<?, ?> record : records) {