### Environment

* Dubbo version: 2.7.6-SNAPSHOT
* Operating System version: Mac
* Java version: 1.8

### Steps to reproduce this issue

run dubbo-samples-simplified-registry-xml 

org.apache.dubbo.samples.simplified.registry.xml.DemoServiceIT
### Expected Result

should pass

### Actual Result

throw exception
private URL providerUrl;
        public InvokerDelegate(Invoker<T> invoker, URL url, URL providerUrl) {
            super(invoker, url);
            this.providerUrl = providerUrl;
        }
        public URL getProviderUrl() {
            return providerUrl;
        }
    }
    private static class ReferenceConfigurationListener extends AbstractConfiguratorListener {
        private RegistryDirectory directory;
        private URL url;
        ReferenceConfigurationListener(RegistryDirectory directory, URL url) {
            this.directory = directory;
            this.url = url;
            this.initWith(DynamicConfiguration.getRuleKey(url) + CONFIGURATORS_SUFFIX);
        }
        void stop() {
            this.stopListen(DynamicConfiguration.getRuleKey(url) + CONFIGURATORS_SUFFIX);
        }
        @Override
        protected void notifyOverrides() {
            
            directory.refreshInvoker(Collections.emptyList());
        }
    }
    private static class ConsumerConfigurationListener extends AbstractConfiguratorListener {