worker: do not send message if port is closing

Fixes: #42296

Author: Trott

src/node_messaging.cc

@@ -980,7 +980,7 @@ void MessagePort::PostMessage(const FunctionCallbackInfo<Value>& args) {
   // Even if the backing MessagePort object has already been deleted, we still
   // want to serialize the message to ensure spec-compliant behavior w.r.t.
   // transfers.
-  if (port == nullptr) {
+  if (port == nullptr || port->IsHandleClosing()) {
     Message msg;
     USE(msg.Serialize(env, context, args[0], transfer_list, obj));
     return;

test/parallel/test-worker-message-port-close.js

@@ -39,3 +39,10 @@ function dummy() {}
     message: 'Cannot send data on closed MessagePort'
   });
 }
+
+{
+  const ch = new MessageChannel()
+  ch.port1.onmessage = common.mustNotCall();
+  ch.port2.close();
+  ch.port2.postMessage('fhqwhgads');
+}