Sonar Fixes

Author: garyrussell

spring-kafka/src/main/java/org/springframework/kafka/listener/BackOffHandler.java

@@ -46,7 +46,7 @@ default void onNextBackOff(@Nullable MessageListenerContainer container, Excepti
 	 * @param partition the partition.
 	 * @param nextBackOff the next back off.
 	 */
-	default void onNextBackOff(@Nullable MessageListenerContainer container, TopicPartition partition,
+	default void onNextBackOff(MessageListenerContainer container, TopicPartition partition,
 			long nextBackOff) {
 
 		throw new UnsupportedOperationException();

spring-kafka/src/main/java/org/springframework/kafka/listener/ListenerContainerPauseService.java

@@ -137,8 +137,11 @@ public void resume(@NonNull MessageListenerContainer messageListenerContainer) {
 		}
 	}
 
+	/*
+	 * Callers must ensure this.registry is not null before calling.
+	 */
 	private Optional<MessageListenerContainer> getListenerContainer(String listenerId) {
-		MessageListenerContainer messageListenerContainer = this.registry.getListenerContainer(listenerId);
+		MessageListenerContainer messageListenerContainer = this.registry.getListenerContainer(listenerId); // NOSONAR
 		if (messageListenerContainer == null) {
 			LOGGER.warn(() -> "MessageListenerContainer " + listenerId + " does not exists");
 		}