NPE throws from WSEndpointMetrics

When upgrade org.wildfly.arquillian:wildfly-arquillian-container-managed to 5.0.0.Alpha6 in jbossws-cxf, the JMSEndpointAPITestCase is failed by the wildfly-arquillian-container-managed sent a failed operation when deploy the archive to server:

{"operation" => "read-attribute","address" => [("deployment" => "jaxws-cxf-jms-api.war"),("subsystem" => "webservices"),("endpoint" => "jaxws-cxf-jms-api%3Aorg.jboss.test.ws.jaxws.cxf.jms.HelloWorldImpl")],"name" => "response-count","include-defaults" => true,"resolve-expressions" => false,"include-undefined-metric-values" => false,"operation-headers" => {"caller-type" => "user","access-mechanism" => "NATIVE"}}

From sever side, it turns out that metrics request is coming but WSEndpointMetrics is not ready because the EndpiontService hasn't finished installing WSEndpointMetrics to ws endpoint. This leads a NPE thrown from WSEndpointMetrics.
We need to add NPE check for WSEndpointMetrics before getting the metric value.