worker: fix crash when a worker joins after exit

If a worker has not already joined before running to completion
it will join in a SetImmediateThreadsafe which could occur after
the worker has already ended by other means. Mutating a JS object
at that point would fail because the isolate is already disposed.

PR-URL: #56191
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

src/node_worker.cc

@@ -449,6 +449,9 @@ void Worker::JoinThread() {
 
   env()->remove_sub_worker_context(this);
 
+  // Join may happen after the worker exits and disposes the isolate
+  if (!env()->can_call_into_js()) return;
+
   {
     HandleScope handle_scope(env()->isolate());
     Context::Scope context_scope(env()->context());