Hey Gaetano,
Thank you for reaching out to us!
Unfortunately this is a known issue. I’ll mark this ticket as Pending Fix, which means this thread should receive a reply once the applicable fix has been released.
I cannot guarantee when it will be fixed, as it’s in the development team’s hands now, but the good news is that you will be contacted as soon as a fix is available.
In the meantime, if you want to hide this PHP Notice, you can simply disable WP_DEBUG or set ‘WP_DEBUG_DISPLAY’ to false.
Thanks for your understanding and if you have any other questions, please let me know and I’ll be happy to assist!
Best Regards,
Patricia