fix: prevent double done() call in TCP request node close handler

Use a guard flag to prevent done() from being called multiple times.
This handles the case where:
- If connected: destroy() triggers close event -> callDone()
- If not connected: callDone() is called directly as safety net
- Guard prevents double-call if close event fires after direct call

Addresses review feedback from @knolleary.

Fixes #5452

packages/node_modules/@node-red/nodes/core/network/31-tcpin.js

@@ -190,11 +190,23 @@ module.exports = function(RED) {
             setupTcpClient();
 
             this.on('close', function(done) {
-                node.doneClose = done;
+                var doneCalled = false;
+                var callDone = function() {
+                    if (!doneCalled) {
+                        doneCalled = true;
+                        done();
+                    }
+                };
+                node.doneClose = callDone;
                 this.closing = true;
-                if (client) { client.destroy(); }
                 clearTimeout(reconnectTimeout);
-                if (!node.connected) { done(); }
+                if (client) {
+                    client.destroy();
+                    // If not connected, close event may not fire, so call done as safety net
+                    if (!node.connected) { callDone(); }
+                } else {
+                    callDone();
+                }
             });
         }
         else {