Load plugin’s CSS file only when widget is used

Hi.
In order to load the CSS file only when the widget is used, please change the function ESR_Official_Widget_for_wordpress_custom_Styling() into:

function ESR_Official_Widget_for_wordpress_custom_Styling(){
	if ( is_active_widget( false, false, 'ersradio-widget', true ) ) {
    // Register my custom stylesheet
    wp_register_style('volumeSliderStyling', plugins_url('ersradio-widget/widgetStyling.css'));
    // Load my custom stylesheet
    wp_enqueue_style('volumeSliderStyling');
	}
}