Error after plugin update

Dear Sirs,

After last plugin update I receive next message:

Fatal error: Uncaught Error: call_user_func_array(): Argument #1 ($callback) must be a valid callback, non-static method Decent_Comments_Widget::cache_delete() cannot be called statically in /var/www/…/htdocs/wp-includes/class-wp-hook.php on line 30

Could you be so kind to fix it.

Thanks.