Windows Phone 7 Wrappanel visibility

public class PhotoConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        try
        {
            if ((value is byte[]) && (value != null))
                return Visibility.Visible;
            else
                return Visibility.Collapsed;
        }

        catch (Exception ex)
        {
            throw ex;
            return Visibility.Collapsed;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

<controls:PanoramaItem x:Name="Pano_Photos" Header="photos">
    <ListBox x:Name="lstMemoriesPhoto" ItemsSource="{Binding MemoryList}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="SelectionChanged" x:Name="ListPhotoSelectionChangedEventTrigger">
                <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding NavigateToDetailPage}" PassEventArgsToCommand="True"/>
            </i:EventTrigger>
        </i:Interaction.Triggers>
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <toolkit:WrapPanel ItemWidth="130" ItemHeight="130"/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Image Source="{Binding MemoryPhoto,Converter={StaticResource ByteImageConverter}}" Visibility="{Binding MemoryPhoto, Converter={StaticResource PhotoConverter}}" Margin="5"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>        
</controls:PanoramaItem>