PHP Notice after updating to 0.8.2.6

After I updated the plugin to version 0.8.2.6 with wp_debug on, I get this php notice:

Notice: Undefined index: page in .../wp-content/plugins/regenerate-thumbnails-advanced/regenerate-thumbnails-advanced.php on line 223

I opened the file at that line, and here’s what I saw:

if (!isset($_GET['page']) && isset($hook)) {
    if ($_GET['page'] !== 'regenerate_thumbnails_advanced' && $hook != 'options-general.php ') {
        return;
    }
}

So, first you check if $_GET[‘page’] is NOT set, and if that’s true, then you check if $_GET[‘page’] is different from ‘regenerate_thumbnails_advanced’. Why is that? Also, not sure whether the space in ‘options-general.php ‘ is intentional or not.

https://www.ads-software.com/plugins/regenerate-thumbnails-advanced/