DUBBO-470 zookeeper注册中心添加empty协议条件错误

dubbo-registry/dubbo-registry-zookeeper/src/main/java/com/alibaba/dubbo/registry/zookeeper/ZookeeperRegistry.java

@@ -263,10 +263,11 @@ public class ZookeeperRegistry extends FailbackRegistry {
 
     private List<URL> toUrlsWithEmpty(URL consumer, String path, List<String> providers) {
         List<URL> urls = toUrlsWithoutEmpty(consumer, providers);
-        if (urls != null && urls.isEmpty()) {
+        if (urls == null || urls.isEmpty()) {
         	int i = path.lastIndexOf('/');
         	String category = i < 0 ? path : path.substring(i + 1);
-            urls.add(URL.valueOf(Constants.EMPTY_PROTOCOL + "://0.0.0.0/" + consumer.getServiceInterface() + "?" + Constants.CATEGORY_KEY + "=" + category));
+        	URL empty = consumer.setProtocol(Constants.EMPTY_PROTOCOL).addParameter(Constants.CATEGORY_KEY, category);
+            urls.add(empty);
         }
         return urls;
     }