### 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 get_v_scroll();
}
void EditorInspector::set_use_wide_editors(bool p_enable) {
	wide_editors = p_enable;
}
void EditorInspector::_update_inspector_bg() {
	if (sub_inspector) {
		int count_subinspectors = 0;
		Node *n = get_parent();
		while (n) {
			EditorInspector *ei = Object::cast_to<EditorInspector>(n);
			if (ei && ei->sub_inspector) {
				count_subinspectors++;
			}
			n = n->get_parent();
		}
		count_subinspectors = MIN(15, count_subinspectors);
		add_theme_style_override("panel", get_theme_stylebox("sub_inspector_bg" + itos(count_subinspectors), SNAME("Editor")));
	} else {
		add_theme_style_override("panel", get_theme_stylebox(SNAME("panel"), SNAME("Tree")));
	}
}
void EditorInspector::set_sub_inspector(bool p_enable) {
	sub_inspector = p_enable;
	if (!is_inside_tree()) {
		return;
	}
	_update_inspector_bg();
}
void EditorInspector::set_use_deletable_properties(bool p_enabled) {