Fixed an NPE (apparently harmless) for a certain connection

teardown ordering and added some logging just to be sure
the channels are getting closed.


git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@7153 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/networking/com/jme3/network/kernel/tcp/SelectorKernel.java

@@ -318,7 +318,13 @@ public class SelectorKernel extends AbstractKernel
 
         protected void cancel( NioEndpoint p ) throws IOException
         {
+            log.log( Level.INFO, "Closing endpoint:{0}.", p );
             SelectionKey key = endpointKeys.remove(p);
+            if( key == null ) {
+                log.log( Level.INFO, "Endpoint already closed:{0}.", p );
+                return;  // already closed it
+            }                
+
             SocketChannel c = (SocketChannel)key.channel();
 
             // Note: key.cancel() is specifically thread safe.  One of
@@ -332,6 +338,7 @@ public class SelectorKernel extends AbstractKernel
         protected void cancel( SelectionKey key, SocketChannel c ) throws IOException
         {
             NioEndpoint p = (NioEndpoint)key.attachment();
+            log.log( Level.INFO, "Closing channel endpoint:{0}.", p );
             endpointKeys.remove(p);
 
             key.cancel();