Merge pull request #22382 from artembilan

* pr/22382:
  Polish contribution
  Polish warning message

spring-messaging/src/main/java/org/springframework/messaging/core/GenericMessagingTemplate.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -354,7 +354,7 @@ public class GenericMessagingTemplate extends AbstractDestinationResolvingMessag
 
 			if (errorDescription != null) {
 				if (logger.isWarnEnabled()) {
-					logger.warn(errorDescription + ":" + message);
+					logger.warn(errorDescription + ": " + message);
 				}
 				if (this.throwExceptionOnLateReply) {
 					throw new MessageDeliveryException(message, errorDescription);