Undefined index: HTTP_USER_AGENT

My error logs are being spammed by this message: Undefined index: HTTP_USER_AGENT. The plugin is being loaded during WP-CLI calls, so $_SERVER['HTTP_USER_AGENT'] doesn’t exist.

This is specifically happening at in Photonic_Plugin\Core\Photonic::__construct in the file Core/Photonic.php, line 20. Please update this, and any other usages of $_SERVER to account for the fact that they may be running outside of the browser context.