fixup! src: restrict unloading addons to Worker threads

src/env.cc

@@ -276,6 +276,11 @@ Environment::~Environment() {
   TRACE_EVENT_NESTABLE_ASYNC_END0(
     TRACING_CATEGORY_NODE1(environment), "Environment", this);
 
+  // Do not unload addons on the main thread. Some addons need to retain memory
+  // beyond the Environment's lifetime, and unloading them early would break
+  // them; with Worker threads, we have the opportunity to be stricter.
+  // Also, since the main thread usually stops just before the process exits,
+  // this is far less relevant here.
   if (!is_main_thread()) {
     // Dereference all addons that were loaded into this environment.
     for (binding::DLib& addon : loaded_addons_) {

test/addons/worker-addon/binding.cc

@@ -49,7 +49,8 @@ void Initialize(Local<Object> exports,
     // the Environment instance has been destroyed.
     static uv_async_t extra_async;
     uv_loop_t* loop = node::GetCurrentEventLoop(context->GetIsolate());
-    uv_async_init(loop, &extra_async, [](uv_async_t*) {});
+    int err = uv_async_init(loop, &extra_async, [](uv_async_t*) {});
+    assert(err == 0);
     uv_unref(reinterpret_cast<uv_handle_t*>(&extra_async));
   }
 }