Dubbo Version: 3.0.10
注册失败，unexport时，subscribeUrl和registerUrl此时为空，需要判断空处理。 
<img width="944" alt="image" src="https://user-images.githubusercontent.com/12670328/200469537-41a4ccb5-adda-4231-9f71-9af9fec2172d.png">


if (register) {
            register(registry, registeredProviderUrl);
        }
        
        registerStatedUrl(registryUrl, registeredProviderUrl, register);
        exporter.setRegisterUrl(registeredProviderUrl);
        exporter.setSubscribeUrl(overrideSubscribeUrl);
        if (!registry.isServiceDiscovery()) {
            
            registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
        }
        notifyExport(exporter);
        
        return new DestroyableExporter<>(exporter);
    }
    private <T> void notifyExport(ExporterChangeableWrapper<T> exporter) {
        ScopeModel scopeModel = exporter.getRegisterUrl().getScopeModel();
        List<RegistryProtocolListener> listeners = ScopeModelUtil.getExtensionLoader(RegistryProtocolListener.class, scopeModel)
            .getActivateExtension(exporter.getOriginInvoker().getUrl(), REGISTRY_PROTOCOL_LISTENER_KEY);
        if (CollectionUtils.isNotEmpty(listeners)) {
            for (RegistryProtocolListener listener : listeners) {
                listener.onExport(this, exporter);
            }
        }
    }
    private URL overrideUrlWithConfig(URL providerUrl, OverrideListener listener) {
        ProviderConfigurationListener providerConfigurationListener = getProviderConfigurationListener(providerUrl);
        providerUrl = providerConfigurationListener.overrideUrl(providerUrl);
        ServiceConfigurationListener serviceConfigurationListener = new ServiceConfigurationListener(providerUrl.getOrDefaultModuleModel(), providerUrl, listener);
        serviceConfigurationListeners.put(providerUrl.getServiceKey(), serviceConfigurationListener);