Hide NewItemPlaceHolder in ListBox WPF

WPF

I have a problem with DataGrid and ListBox. Users can add new rows to datagrid, but an empty row is visible in listbox.

I found info about NewItemPlaceHolder, but I don't know how to hide it in listbox.

Please, help me! :D

XAML:

ListBox AlternationCount="2" ItemContainerStyle="{StaticResource alternatingWithTriggers}" x:Name="ViewListBox" Background="AliceBlue" ItemsSource="{Binding Converter={StaticResource IgnoreNewItemPlaceholderConverter}}"

CS:

    public static readonly IgnoreNewItemPlaceholderConverter Instance = new IgnoreNewItemPlaceholderConverter();

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
            if (value != null && value.ToString() == "{NewItemPlaceholder}")
            {

                return DependencyProperty.UnsetValue;
            }
            MessageBox.Show(value.ToString());
            return value;


    }