### Environment

* Dubbo version: 3.0
StaticDirectory.destroy方法最后要对列表做clear操作，但是ReferenceConfig的createInvokerForLocal构造StaticDirectory传入的列表类型是Collections.singletonList，执行clear就会抛异常：
```
[08/10/21 07:35:39:302 UTC] main  WARN config.ReferenceConfig:  [DUBBO] Unexpected error occurred when destroy invoker of ReferenceConfig(null)., dubbo version: 3.0.4-SNAPSHOT, current host: 172.19.112.1
java.lang.UnsupportedOperationException
	at java.util.AbstractList.remove(AbstractList.java:161)
	at java.util.AbstractList$Itr.remove(AbstractList.java:374)
	at java.util.AbstractList.removeRange(AbstractList.java:571)
	at java.util.AbstractList.clear(AbstractList.java:234)
	at org.apache.dubbo.rpc.cluster.directory.StaticDirectory.destroy(StaticDirectory.java:91)
	at org.apache.dubbo.rpc.cluster.support.AbstractClusterInvoker.destroy(AbstractClusterInvoker.java:113)
	at org.apache.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.destroy(MockClusterInvoker.java:79)
	at org.apache.dubbo.config.ReferenceConfig.destroy(ReferenceConfig.java:219)
```
boolean isJvmRefer;
        if (isInjvm() == null) {
            // 
            if (StringUtils.isNotEmpty(url)) {
                isJvmRefer = false;
            } else {
                // 
                isJvmRefer = InjvmProtocol.getInjvmProtocol(getScopeModel()).isInjvmRefer(tmpUrl);
            }
        } else {
            isJvmRefer = isInjvm();
        }
        return isJvmRefer;
    }
    private void postProcessConfig() {
        List<ConfigPostProcessor> configPostProcessors = this.getExtensionLoader(ConfigPostProcessor.class)
            .getActivateExtension(URL.valueOf("configPostProcessor://"), (String[]) null);
        configPostProcessors.forEach(component -> component.postProcessReferConfig(this));
    }
    /**
     * just for test
     *
     * @return
     */
    @Deprecated
    public Invoker<?> getInvoker() {
        return invoker;
    }
}