Appointments+ conflict with Woocommerce Point Of Sale

I'm attempting to use a newish plugin from CodeCanyon called WooCommerce Point Of Sale.

I'm getting a Fatal Error from your plugin when i try to load the Register for the POS plugin.

Fatal error: Call to undefined function get_current_screen() in .../wp-content/plugins/appointments/appointments.php on line 4929

I've notified the developer of the POS plugin but since this is a Fatal Error for Appointments+ i thought you should know.

Let me know if you need more info. I would like to use Appointments+ as well as the POS!