I am new here and I have a question, I hope you can help me. Received this error from the WordPress plugin wp-postratings
Notice: Undefined variable: thumbnail in /storage/emulated/legacy/htdocs/wp-content/plugins/wp-postratings/wp-postratings.php on line 1176
This is the file in conflict: link
Unless you see an error or problem in the functionality of the plugin, you should ignore this message, which is not an error, but a "warning" or "Notice".
So that these messages are not shown on your web page in production, you should disable the WordPress debug mode and that PHP should display errors on the page:
define( 'WP_DEBUG', false );
ini_set( 'display_errors', false );