### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Window 11, Forward+, GTX 1060

### Issue description

Adding two theme variations in a row result to a  crash.

https://user-images.githubusercontent.com/93253123/217037249-1ce1d56d-beb6-4435-83ad-9f8a07fe0e96.mp4



### Steps to reproduce

1. Create a project.
2. Create a theme.
3. Double click to go in the theme editor.
4. Click on manage items buttons.
5. In the add type field type a name to add a type.
6. type another name to add a second type.
7. Crash.

### Minimal reproduction project

[ThemeVariationCrash.zip](https://github.com/godotengine/godot/files/10665863/ThemeVariationCrash.zip)

add_meta_error = memnew(Label);
		vbc->add_child(add_meta_error);
		add_meta_name->connect("text_changed", callable_mp(this, &EditorInspector::_check_meta_name));
	}
	Node *node = Object::cast_to<Node>(object);
	if (node) {
		add_meta_dialog->set_title(vformat(TTR("Add Metadata Property for \"%s\""), node->get_name()));
	} else {
		
		add_meta_dialog->set_title(vformat(TTR("Add Metadata Property for \"%s\""), object->get_class()));
	}
	add_meta_dialog->popup_centered();
	add_meta_name->set_text("");
	_check_meta_name("");
	add_meta_name->grab_focus();
}
void EditorInspector::_bind_methods() {
	ClassDB::bind_method("_edit_request_change", &EditorInspector::_edit_request_change);
	ClassDB::bind_method("get_selected_path", &EditorInspector::get_selected_path);
	ADD_SIGNAL(MethodInfo("property_selected", PropertyInfo(Variant::STRING, "property")));
	ADD_SIGNAL(MethodInfo("property_keyed", PropertyInfo(Variant::STRING, "property"), PropertyInfo(Variant::NIL, "value", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NIL_IS_VARIANT), PropertyInfo(Variant::BOOL, "advance")));
	ADD_SIGNAL(MethodInfo("property_deleted", PropertyInfo(Variant::STRING, "property")));
	ADD_SIGNAL(MethodInfo("resource_selected", PropertyInfo(Variant::OBJECT, "resource", PROPERTY_HINT_RESOURCE_TYPE, "Resource"), PropertyInfo(Variant::STRING, "path")));
	ADD_SIGNAL(MethodInfo("object_id_selected", PropertyInfo(Variant::INT, "id")));
	ADD_SIGNAL(MethodInfo("property_edited", PropertyInfo(Variant::STRING, "property")));
	ADD_SIGNAL(MethodInfo("property_toggled", PropertyInfo(Variant::STRING, "property"), PropertyInfo(Variant::BOOL, "checked")));
	ADD_SIGNAL(MethodInfo("edited_object_changed"));
	ADD_SIGNAL(MethodInfo("restart_requested"));
}
EditorInspector::EditorInspector() {