Error with WooCommerce

Hi, unexpected error when I trie to search in product in Backend WooCommerce:

Notice: Undefined index: action2 in [removed]/plugins/regenerate-thumbnails/regenerate-thumbnails.php on line 121

Warning: Cannot modify header information - headers already sent by (output started at [removed]/plugins/regenerate-thumbnails/regenerate-thumbnails.php:121) in [removed]/wp-includes/pluggable.php on line 896

https://wordpress.org/plugins/regenerate-thumbnails/