Short-circuit PluginUserSession in case a not live jcr session is encountered

Currently, there is code something like

public Session getJcrSession() {
Session session = getJcrSessionInternal();
if (session == null) {

if getJcrSessionInternal() return null, a fallback session is returned in case there are fallbackcredentials.

getJcrSessionInternal() returns the jcrSessionModel.getObject() and if not null also does a check whether the session is live. In case the session is not live, the entire request should be short circuited as this is an illegal state