### 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 vbox;
}
void EditorInspectorSection::unfold() {
	if (!foldable) {
		return;
	}
	_test_unfold();
	object->editor_set_section_unfold(section, true);
	vbox->show();
	queue_redraw();
}
void EditorInspectorSection::fold() {
	if (!foldable) {
		return;
	}
	if (!vbox_added) {
		return;
	}
	object->editor_set_section_unfold(section, false);
	vbox->hide();
	queue_redraw();
}
bool EditorInspectorSection::has_revertable_properties() const {