It appears imath was updated but krita is compiled with the old version.
pacman -Q krita imath
krita 5.2.11-2
imath 3.2.1-1
pacman -Qkk krita imath
krita: 1449 total files, 0 altered files
imath: 108 total files, 0 altered files
-rw-r--r-- 1 root root 4133080 Aug 24 05:15 imath-3.2.1-1-x86_64.pkg.tar.zst
-rw-r--r-- 1 root root 566 Aug 24 05:15 imath-3.2.1-1-x86_64.pkg.tar.zst.sig
-rw-r--r-- 1 root root 67899432 Aug 23 22:41 krita-5.2.11-2-x86_64.pkg.tar.zst
-rw-r--r-- 1 root root 566 Aug 23 22:42 krita-5.2.11-2-x86_64.pkg.tar.zst.sig