Editor crashes on shutdown when fetching a singleton via Engine

[Naros]

Godot version

4.6.beta2

godot-cpp version

4.5.0.stable sync and b724219

System information

Windows 11. I should note that on Linux, I do not observe this behavior, and unfortunately, I do not have a MacOS system to verify whether this problem exists there or not.

Issue description

When using the following logic in an empty GDExtension:

void initialize_extension_module(ModuleInitializationLevel p_level) {
  if (p_level == MODULE_INITIALIZATION_LEVEL_EDITOR) {
    for (const String& singleton_name : Engine::get_singleton()->get_singleton_list()) {
      Object* o = Engine::get_singleton()->get_singleton(singleton_name);
    }
  }
}

On Windows, when the editor closes, this leads to

[0] <couldn't map PC to fn name>
[1] Object::~Object (core\object\object.cpp:2436)
[2] GDExtensionManager::`scalar deleting destructor`
[3] unregister_core_types (core\register_core_types.cpp:427)
[4] Main::cleanup (main\main.cpp:5229)
[5] widechar_main (platform\windows\godot_windows.cpp:105)
[6] _main (platform\windows\godot_windows.cpp:128)
[7] main (platform\windows\godot_windows.cpp:140)

Steps to reproduce

See code snippet above.

Minimal reproduction project

N/A

[Naros]

As discussed in dev chat, this seems to be related to #1458. Apply this in the Engine method call addresses the issue, although we recognize this isn't the right fix

Object* obj = internal::_call_native_mb_ret_obj<Object>(_gde_method_bind, _owner, &p_name);
ClassDB::_register_engine_singleton(p_name, obj);
return obj;

[dsnopek]

On chat, I asked @Naros to test changing Object *Engine::get_singleton(const StringName &) to this code:

Object *Engine::get_singleton(const StringName &p_name) const {
	static GDExtensionMethodBindPtr _gde_method_bind = ::godot::gdextension_interface::classdb_get_method_bind(Engine::get_class_static()._native_ptr(), StringName("get_singleton")._native_ptr(), 1371597918);
	CHECK_METHOD_BIND_RET(_gde_method_bind, (nullptr));
	Object *obj = ::godot::internal::_call_native_mb_ret_obj<Object>(_gde_method_bind, _owner, &p_name);
	ClassDB::_register_engine_singleton(p_name, singleton);
	return obj;
}

... and he said it fixed the issue for him!

So, I think the problem is that the fix we added in #1458 only applied to the classes static get_singleton() methods and we need to make sure the same applies to Object *Engine::get_singleton(const StringName &)

UPDATE: Oops, cross post :-)