NPE when start dubbo-admin

[wxbty]

• I have searched the issues of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 3.1.2
• Operating System version: mac m1
• Java version: 1.8

Steps to reproduce this issue

1. git clone https://github.com/apache/dubbo-admin.git default in develop branch
2. run DubboAdminApplication.main

Expected Behavior

start success

Actual Behavior

NPE error

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

2022-12-22 17:12:14.849  INFO 10532 --- [           main] o.a.d.r.zookeeper.ZookeeperRegistry      :  [DUBBO] Notify urls for subscribe url admin://10.169.1.114/org.apache.dubbo.metadata.MetadataService?category=providers,consumers,routers,configurators&check=false&classifier=*&enabled=*&group=*&interface=org.apache.dubbo.metadata.MetadataService&version=*, url size: 4, dubbo version: 3.1.2, current host: 10.169.1.114
2022-12-22 17:12:15.212 ERROR 10532 --- [-30880-thread-1] o.a.dubbo.rpc.filter.ExceptionFilter     :  [DUBBO] Got unchecked and undeclared exception which called by 10.169.1.114. service: org.apache.dubbo.metadata.MetadataService, method: getSubscribedURLs, exception: java.lang.NullPointerException: null, dubbo version: 3.1.2, current host: 10.169.1.114, error code: 5-36. This may be caused by , go to https://dubbo.apache.org/faq/5/36 to find instructions. 

java.lang.NullPointerException: null
	at org.apache.dubbo.registry.client.metadata.MetadataServiceDelegation.getAllUnmodifiableSubscribedURLs(MetadataServiceDelegation.java:117)
	at org.apache.dubbo.registry.client.metadata.MetadataServiceDelegation.getSubscribedURLs(MetadataServiceDelegation.java:88)
	at org.apache.dubbo.registry.client.metadata.MetadataServiceDelegationDubboWrap1.invokeMethod(MetadataServiceDelegationDubboWrap1.java)
	at org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:73)
	at org.apache.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:100)
	at org.apache.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke(DelegateProviderMetaDataInvoker.java:55)
	at org.apache.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56)
	at org.apache.dubbo.rpc.filter.ClassLoaderCallbackFilter.invoke(ClassLoaderCallbackFilter.java:38)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:79)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:45)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:100)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.ExecuteLimitFilter.invoke(ExecuteLimitFilter.java:59)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:54)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:192)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:54)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:41)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.ProfilerServerFilter.invoke(ProfilerServerFilter.java:57)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:133)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CopyOfFilterChainNode.invoke(FilterChainBuilder.java:327)
	at org.apache.dubbo.rpc.cluster.filter.FilterChainBuilder$CallbackRegistrationInvoker.invoke(FilterChainBuilder.java:194)
	at org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:156)
	at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:102)
	at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:177)
	at org.apache.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:53)
	at org.apache.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:61)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.dubbo.common.threadlocal.InternalRunnable.run(InternalRunnable.java:41)
	at java.lang.Thread.run(Thread.java:750)

Through debug, this bug comes from dubbo