nezzie Do you have the previous qtvurve version in your pacman cache? If so, please check if that fixes this issue, will rebuild a downgraded version.
It fixes this here.
Version needed is qtcurve-1.8.18.13-1-x86_64.pkg.tar.xz
If in your cache:
sudo pacman -U /var/cache/pacman/pkg/qtcurve-1.8.18.13-1-x86_64.pkg.tar.xz
If not available, let me know too, I can upload this version in a temp location then.