### 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)

return object_class;
}
void EditorInspector::_feature_profile_changed() {
	update_tree();
}
void EditorInspector::set_restrict_to_basic_settings(bool p_restrict) {
	restrict_to_basic = p_restrict;
	update_tree();
}
void EditorInspector::set_property_clipboard(const Variant &p_value) {
	property_clipboard = p_value;
}
Variant EditorInspector::get_property_clipboard() const {
	return property_clipboard;
}
void EditorInspector::_add_meta_confirm() {
	String name = add_meta_name->get_text();
	object->editor_set_section_unfold("metadata", true); 
	Variant defval;
	Callable::CallError ce;
	Variant::construct(Variant::Type(add_meta_type->get_selected_id()), defval, nullptr, 0, ce);
	EditorUndoRedoManager *undo_redo = EditorUndoRedoManager::get_singleton();
	undo_redo->create_action(vformat(TTR("Add metadata %s"), name));
	undo_redo->add_do_method(object, "set_meta", name, defval);
	undo_redo->add_undo_method(object, "remove_meta", name);
	undo_redo->commit_action();
}
void EditorInspector::_check_meta_name(const String &p_name) {