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">


URL newProviderUrl = getUrlToRegistry(newInvokerUrl, registryUrl);
        
        Invoker<T> invokerDelegate = new InvokerDelegate<T>(originInvoker, newInvokerUrl);
        exporter.setExporter(protocol.export(invokerDelegate));
        
        if (!newProviderUrl.equals(registeredUrl)) {
            try {
                doReExport(originInvoker, exporter, registryUrl, registeredUrl, newProviderUrl);
            } catch (Exception e) {
                ReExportTask oldTask = reExportFailedTasks.get(registeredUrl);
                if (oldTask != null) {
                    return;
                }
                ReExportTask task = new ReExportTask(
                    () -> doReExport(originInvoker, exporter, registryUrl, registeredUrl, newProviderUrl),
                    registeredUrl,
                    null
                );
                oldTask = reExportFailedTasks.putIfAbsent(registeredUrl, task);
                if (oldTask == null) {
                    
                    retryTimer.newTimeout(task, registryUrl.getParameter(REGISTRY_RETRY_PERIOD_KEY, DEFAULT_REGISTRY_RETRY_PERIOD), TimeUnit.MILLISECONDS);
                }
            }
        }
    }
    private <T> void doReExport(final Invoker<T> originInvoker, ExporterChangeableWrapper<T> exporter,
                                URL registryUrl, URL oldProviderUrl, URL newProviderUrl) {
        if (getProviderUrl(originInvoker).getParameter(REGISTER_KEY, true)) {
            Registry registry;