Bug 322575 resolve potential NPE in hot swap handler if old handler was null. added a null check since existing doStart and doStop methods specifically handle cases where wrapped handler is null on start/stop

git-svn-id: svn+ssh://dev.eclipse.org/svnroot/rt/org.eclipse.jetty/jetty/trunk@2216 7e9141cc-0065-0410-87d8-b60c137991c4

VERSION.txt

@@ -13,6 +13,7 @@ jetty-7.2-SNAPSHOT
  + 321730 SelectChannelEndPoint prints to System.err
  + 321735 HttpClient onException called for buffer overflow.
  + 322448 Added jetty-dir.css for directory listings
+ + 322575 NPE in HotSwapHandler if old handler null
  + 322683 RewriteHandler thread safety
  + JETTY-912 added per exchange timeout api
  + JETTY-1245 Do not use direct buffers with NIO SSL

jetty-server/src/main/java/org/eclipse/jetty/server/handler/HotSwapHandler.java

@@ -80,8 +80,11 @@ public class HotSwapHandler extends AbstractHandlerContainer
 
             _handler = handler;
             
-            if (isStarted())
+            // if there is an old handler and it was started, stop it
+            if (old_handler != null && isStarted())
+            {
                 old_handler.stop();
+            }
 
         }
         catch(RuntimeException e)