OF-2809: Guard against negative max idle time for websockets (#2434)

* OF-2809: Guard against negative max idle time for websockets

When the max idle time is configured to be negative, then do not schedule the check to see if the connection is still active.

* OF-2809: Tweak task implementation to make null-references less likely

... and rename class to follow convention of starting with a capital letter.

xmppserver/src/main/java/org/jivesoftware/openfire/websocket/WebSocketClientConnectionHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 Tom Evans, 2023 Ignite Realtime Foundation. All rights reserved.
+ * Copyright (C) 2015 Tom Evans, 2023-2024 Ignite Realtime Foundation. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -111,8 +111,13 @@ public void onConnect(Session session)
             final Duration taskInterval = KEEP_ALIVE_FRAME_PING_INTERVAL_PROPERTY.getValue().dividedBy(10);
             TaskEngine.getInstance().schedule(websocketFramePingTask, taskInterval, taskInterval);
         }
-        xmppSessionIdleTask = new xmppSessionIdleTask();
-        TaskEngine.getInstance().schedule(xmppSessionIdleTask, getMaxIdleTime().dividedBy(10), getMaxIdleTime().dividedBy(10));
+
+        final Duration maxIdleTime = getMaxIdleTime();
+        xmppSessionIdleTask = new XmppSessionIdleTask();
+        if (!maxIdleTime.isNegative() && !maxIdleTime.isZero()) {
+            TaskEngine.getInstance().schedule(xmppSessionIdleTask, maxIdleTime.dividedBy(10), maxIdleTime.dividedBy(10));
+        }
+
         wsConnection.setStanzaHandler(new WebSocketClientStanzaHandler(XMPPServer.getInstance().getPacketRouter(), wsConnection));
     }
 
@@ -275,13 +280,13 @@ public void run() {
     /**
      * Task that, on prolonged inactivity, sends an XMPP ping, to ensure that the remote entity is still responsive.
      */
-    private final class xmppSessionIdleTask extends TimerTask {
+    private final class XmppSessionIdleTask extends TimerTask {
         private Instant pendingPingSentAt = null;
 
         @Override
         public void run()
         {
-            if (!isWebSocketOpen()) {
+            if (!isWebSocketOpen() || getMaxIdleTime().isNegative() || getMaxIdleTime().isZero()) {
                 TaskEngine.getInstance().cancelScheduledTask(websocketFramePingTask);
                 TaskEngine.getInstance().cancelScheduledTask(xmppSessionIdleTask);
                 return;