twentynineteen_nav_menu_social_icons( string $item_output, WP_Post $item, int $depth, stdClass $args ): string

49function twentynineteen_nav_menu_social_icons( $item_output, $item, $depth, $args ) {50	// Change SVG icon inside social links menu if there is supported URL.51	if ( 'social' === $args->theme_location ) {52		$svg = twentynineteen_get_social_link_svg( $item->url, 32 );53		if ( empty( $svg ) ) {54			$svg = twentynineteen_get_icon_svg( 'link' );55		}56		$item_output = str_replace( $args->link_after, '</span>' . $svg, $item_output );57	}58 59	return $item_output;60}