Fix NPE on shutdown if solr disabled

[gallardo]

No description provided.

[gallardo]

This doesn't look too harmful: a few indexes won't be shutdown, the m_indexes won't be cleared, the non-started SolrContainer won't be shutdown, but the NPE is a bit distracting.

[gallardo]

For the records (and for google): I have tested this today again, and I can confirm that this commit fixes an issue that arises during server shutdown: two threads stall, and the container must be manually killed. In the logs:

ERROR [  org.opencms.main.OpenCmsCore:1790] Error during search manager shutdown: null
java.lang.NullPointerException
    at org.opencms.search.solr.CmsSolrIndex.shutDown(CmsSolrIndex.java:504)
    at org.opencms.search.CmsSearchManager.shutDown(CmsSearchManager.java:2244)
    at org.opencms.main.OpenCmsCore.shutDown(OpenCmsCore.java:1787)
    at org.opencms.main.OpenCmsListener.contextDestroyed(OpenCmsListener.java:66)
    at org.apache.catalina.core.StandardContext.listenerStop(StandardContext.java:4776)
    at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:5390)
    at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:232)
    at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1424)
    at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1413)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
[...] Shutting down [...]
[...] OpenCms stopped!     : Total uptime was [...]
WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [opencms] appears to have started a thread named [searcherExecutor-4-thread-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.misc.Unsafe.park(Native Method)
 java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
 java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
 java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
 java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:745)
WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [opencms] appears to have started a thread named [Thread-6] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Object.wait(Native Method)
 java.lang.Object.wait(Object.java:502)
 org.apache.solr.core.CloserThread.run(CoreContainer.java:2075)