We pass `null` for the class name here:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L261

However the class name is mandatory for the transport protocol today:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L156

This prevents various APIs from working in a cluster with stable plugins installed.
x-pack/plugin/security/src/test/java/org/elasticsearch/test/SecurityIntegTestCase.java
@Before
    
    public void assertXPackIsInstalled() {
        doAssertXPackIsInstalled();
    }
    protected void doAssertXPackIsInstalled() {
        NodesInfoResponse nodeInfos = clusterAdmin().prepareNodesInfo().clear().setPlugins(true).get();
        for (NodeInfo nodeInfo : nodeInfos.getNodes()) {
            
            
            Collection<String> pluginNames = nodeInfo.getInfo(PluginsAndModules.class)
                .getPluginInfos()
                .stream()
                .map(p -> p.descriptor().getClassname())
                .collect(Collectors.toList());
            assertThat(
                "plugin [" + xpackPluginClass().getName() + "] not found in [" + pluginNames + "]",
                pluginNames,
                hasItem(xpackPluginClass().getName())
            );
        }
    }
    protected Class<?> xpackPluginClass() {
        return LocalStateSecurity.class;
    }
    @Override
    protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
        Settings.Builder builder = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));