Fix ResourceHttpRequestHandler empty location log

Fix ResourceHttpRequestHandler to only log warning when locations
is empty.

Issue: SPR-10780
(cherry picked from bc52469)

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -34,6 +34,7 @@ import org.springframework.core.io.Resource;
 import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.FileCopyUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.HttpRequestHandler;
@@ -94,7 +95,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator implements H
 	}
 
 	public void afterPropertiesSet() throws Exception {
-		if (logger.isWarnEnabled()) {
+		if (logger.isWarnEnabled() && CollectionUtils.isEmpty(this.locations)) {
 			logger.warn("Locations list is empty. No resources will be served");
 		}
 	}