486530 - Handler added to WebAppContext prevents ServletContext initialization

Fixed needless warnings during destroy

jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletContextHandler.java

@@ -178,6 +178,7 @@ public class ServletContextHandler extends ContextHandler
     @Override
     public void setHandler(Handler handler)
     {
+        if (handler!=null)
             LOG.warn("ServletContextHandler.setHandler should not be called directly. Use insertHandler or setSessionHandler etc.");
         super.setHandler(handler);
     }