Adding Appsero Fatals Sites.

Adding Appsero for this plugin and click-to-top has caused sites to fatal.

https://plugins.trac.ww.wp.xz.cn/changeset/2497044
https://plugins.trac.ww.wp.xz.cn/changeset/2494177

This is because when adding it you have the require statement reading as:

if ( ! class_exists( 'Appsero\Client' ) ) {
    require_once __DIR__ . '/appsero/src/Client.php';
}

however the path to the appsero client should actually be

require_once __DIR__ . '/vendor/appsero/client/src/Client.php';

You’re trying to require a file that doesn’t exist, so the site dies.