Custom Attribute Code for SiteOrigin Row giving Error Message

I’m using the following code to add a Select field to the Attributes Row:

// Add Custom Class Options to SiteOrigin Rows
add_filter( 'siteorigin_panels_row_style_fields', 'custom_row_style_fields' );
function custom_row_style_fields($fields) {
	$row_styles = array(
		'default-row-style' => 'Choose Style',
		'row-notification' => 'Notification'
	);
		
	$fields['row_styles'] = array(
		'name' => __('Row Styles', 'siteorigin-panels'),
		'type' => 'select',
		'options' => $row_styles,
		'group' => 'attributes',
		'description' => __('Choose a style option for this row of content', 'siteorigin-panels'),
		'priority' => 1,
	);

	return $fields;
}

function custom_row_style_attributes( $attributes, $args ) {
	if( $args['row_styles'] != 'default-row-style' ) {
		array_push($attributes['class'], $args['row_styles'] );
	}

	return $attributes;
}

add_filter('siteorigin_panels_row_style_attributes', 'custom_row_style_attributes', 10, 2);

This code is throwing the following error:

[01-May-2017 13:29:39 UTC] PHP Notice:  Undefined index: row_styles in /xx/xx/xx/wp-content/themes/edmond/functions.php on line 223
[01-May-2017 13:29:39 UTC] PHP Notice:  Undefined index: row_styles in /xx/xx/xx/wp-content/themes/edmond/functions.php on line 224

Line 223 is if( $args['row_styles'] != 'default-row-style' ) {
Line 224 is array_push($attributes['class'], $args['row_styles'] );

Any ideas why?