can't create valid licenses

I have made a test license which first decodes JSON is. The Signature is an empty string
{"authority_signature":"","expiry_date":1612447411,"issue_date":1580911411

and validating the file fails with:
Failed to verify the licensing authority

In case someone has the same problem, it's coming from a bug in the copy constructor of License class. It has been fixed here: cd4706f