StandardListView current_item member allows invalid index

[JaberwockySeamonstah]

Bug Description

The code below creates a simple StandardListView with 3 elements and a button to remove the currently selected element from that StandardListView. The element will be removed via the attached Rust code.

To reproduce the issue, just select the last element (Green) and click the button. The element will disappear as expected. Since no element is selected anymore, I assumed the value is -1, instead it is still 2. So clicking the button again, will make the application panic.

I understand, that I can reset the value manual to -1 or any other logical value, but I was surprised to find, that this simple setup would allow me to panic.

Reproducible Code (if applicable)

import { Button, StandardListView } from "std-widgets.slint";
export component MainWindow inherits Window {
    in-out property <[StandardListViewItem]> items: [{ text: "Blue" }, { text: "Red" }, { text: "Green" }];
    callback remove_item(int);

    VerticalLayout {
        list_view := StandardListView {
            width: 320px;
            height: 256px;
            model: root.items;
        }
        Button {
            text: "Click";
            clicked => {
                root.remove_item(list_view.current-item);
            }
        }        
    }
}

// Rust Code
#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]

use slint::Model;
slint::include_modules!();

fn main() -> Result<(), slint::PlatformError> {
    let main_window      = MainWindow::new()?;

    let items:Vec<slint::StandardListViewItem> = main_window.get_items().iter().collect();
    let items                                  = std::rc::Rc::new(slint::VecModel::from(items));
    let main_window_weak                       = main_window.as_weak();

    main_window.on_remove_item(move |idx: i32| {
        if idx >= 0 {
            items.remove(idx as usize);
            main_window_weak.unwrap().set_items(items.clone().into());
        }
    });
    main_window.run()
}

Environment Details

• Slint Version: 1.9.2
• Platform/OS: Linux, KDE, Wayland
• Programming Language: Rust
• Backend/Renderer: No idea, probably the default

Product Impact

I'm building an open-source application with slint, it is my first slint project. This issue is a minor one, because there are simple workarounds.