### 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)

vbox = memnew(VBoxContainer);
	dropping_unfold_timer = memnew(Timer);
	dropping_unfold_timer->set_wait_time(0.6);
	dropping_unfold_timer->set_one_shot(true);
	add_child(dropping_unfold_timer);
	dropping_unfold_timer->connect("timeout", callable_mp(this, &EditorInspectorSection::unfold));
}
EditorInspectorSection::~EditorInspectorSection() {
	if (!vbox_added) {
		memdelete(vbox);
	}
}
int EditorInspectorArray::_get_array_count() {
	if (mode == MODE_USE_MOVE_ARRAY_ELEMENT_FUNCTION) {
		List<PropertyInfo> object_property_list;
		object->get_property_list(&object_property_list);
		return _extract_properties_as_array(object_property_list).size();
	} else if (mode == MODE_USE_COUNT_PROPERTY) {
		bool valid;
		int count_val = object->get(count_property, &valid);
		ERR_FAIL_COND_V_MSG(!valid, 0, vformat("%s is not a valid property to be used as array count.", count_property));
		return count_val;
	}
	return 0;
}
void EditorInspectorArray::_add_button_pressed() {