https://wccftech.com/macos-catalina-10-15-4-supplemental-update-released-with-facetime-fix/

Apple has just released macOS Catalina 10.15.4 Supplemental Update with fix for FaceTime bug along with amongst other things.

Having already released iOS 13.4.1 / iPadOS 13.4.1 and watchOS 6.2.1, Apple has now seeded the macOS Catalina 10.15.4 Supplemental Update to users to fix the unsurprising FaceTime bug.