Undefined variable $css_class

In master-slider/admin/includes/classes/class-msp-shortcode-factory.php, MSP_Shortcode_Factory::get_ms_slide_info_shortcode() method, the $css_class is undefined if slide info is anything other than empty string. Please initialize the variable so that it doesn’t throw notices:

if( !$the_content )
    return '';

$css_class = ( " " == $the_content ) ? 'ms-info-empty' : '';
return sprintf( '[%1$s css_class="%3$s"]%2$s[/%1$s]', 'ms_slide_info', $the_content, $css_class )."\n";

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