export broken

when you try to export rules, errors are thrown instead.

Notice: ob_end_clean(): failed to delete buffer. No buffer to delete in /wp-content/plugins/woo-discount-rules/v2/App/Controllers/ManageDiscount.php on line 2417

Warning: Cannot modify header information - headers already sent by (output started at /wp-content/plugins/woo-discount-rules/v2/App/Controllers/ManageDiscount.php:2417) in /wp-content/plugins/woo-discount-rules/v2/App/Controllers/ManageDiscount.php on line 2422

Warning: Cannot modify header information - headers already sent by (output started at /wp-content/plugins/woo-discount-rules/v2/App/Controllers/ManageDiscount.php:2417) in /wp-content/plugins/woo-discount-rules/v2/App/Controllers/ManageDiscount.php on line 2423