The reason behind this is the recent icu upgrade, firedragon (and lots of other packages using this library such as ungoogled-chromium, thunderbird-appmenu) needed a rebuild as the shared library changed. Actually I forgot to raise pkgrel when rebuilding - the solution is therefore:
sudo pacman -Syu firedragon
The AUR PKGBUILDs are not up to date as Im currently waiting for a TU to approve pending requests regarding package name changes which were explained in the FireDragon thread 