### Godot version

4.1 rc3

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

This™
![image](https://github.com/godotengine/godot/assets/2223172/cb33110f-a5b0-400a-951f-3fa425f05714)

It can still happen, but it's more difficult to trigger.

### Steps to reproduce

1. Create a new scene with a Control node
2. Add Theme to the Control
3. Open Theme Editor
4. Clear the `theme` property in Control
5. Save, with Theme Editor opened
6. Restart

### Minimal reproduction project

N/A
immediate_dialog_confirmed = true;
}
bool EditorNode::immediate_confirmation_dialog(const String &p_text, const String &p_ok_text, const String &p_cancel_text) {
	ConfirmationDialog *cd = memnew(ConfirmationDialog);
	cd->set_text(p_text);
	cd->set_ok_button_text(p_ok_text);
	cd->set_cancel_button_text(p_cancel_text);
	cd->connect("confirmed", callable_mp(singleton, &EditorNode::_immediate_dialog_confirmed));
	singleton->gui_base->add_child(cd);
	cd->popup_centered();
	while (true) {
		OS::get_singleton()->delay_usec(1);
		DisplayServer::get_singleton()->process_events();
		Main::iteration();
		if (singleton->immediate_dialog_confirmed || !cd->is_visible()) {
			break;
		}
	}
	memdelete(cd);
	return singleton->immediate_dialog_confirmed;
}
void EditorNode::cleanup() {
	_init_callbacks.clear();
}
int EditorNode::get_current_tab() {