- [ ] I have searched the [issues](https://github.com/apache/incubator-dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/incubator-dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: xxx
* Operating System version: xxx
* Java version: xxx

### Steps to reproduce this issue

1. xxx
2. xxx
3. xxx

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

if (CollectionUtils.isEmptyMap(newUrlInvokerMap)) {
                logger.error(new IllegalStateException("urls to invokers error .invokerUrls.size :" + invokerUrls.size() + ", invoker.size :0. urls :" + invokerUrls
                        .toString()));
                return;
            }
            List<Invoker<T>> newInvokers = Collections.unmodifiableList(new ArrayList<>(newUrlInvokerMap.values()));
            
            
            routerChain.setInvokers(newInvokers);
            this.invokers = multiGroup ? toMergeInvokerList(newInvokers) : newInvokers;
            this.urlInvokerMap = newUrlInvokerMap;
            try {
                destroyUnusedInvokers(oldUrlInvokerMap, newUrlInvokerMap); 
            } catch (Exception e) {
                logger.warn("destroyUnusedInvokers error. ", e);
            }
        }
    }
    private List<Invoker<T>> toMergeInvokerList(List<Invoker<T>> invokers) {
        List<Invoker<T>> mergedInvokers = new ArrayList<>();
        Map<String, List<Invoker<T>>> groupMap = new HashMap<String, List<Invoker<T>>>();
        for (Invoker<T> invoker : invokers) {
            String group = invoker.getUrl().getParameter(Constants.GROUP_KEY, "");
            groupMap.computeIfAbsent(group, k -> new ArrayList<>());
            groupMap.get(group).add(invoker);
        }
        if (groupMap.size() == 1) {
            mergedInvokers.addAll(groupMap.values().iterator().next());
        } else if (groupMap.size() > 1) {