Error posts list attribute

Hi,

I’m trying to create a custom widget. 
I have an error: “Uncaught Error: Undefined input: undefined” when I try to add the posts list attribute and “Use Custom Fields”.

I have already sent a ticket on https://unitecms.ticksy.com/ but it was 3 weeks ago and I still don’t have a solution.

https://postimg.cc/SnxmybjN

Could you please help?