Manjaro-mate-settings depends on removed adapta-maia-theme.
In line 26 of manjaro-mate-settings PKGBUILD, you can see:
'adapta-maia-theme'
But this package doesn't exist anymore.
[fred@fredo-manja-mate ~]$ pacman -Ss adapta-maia-theme
[fred@fredo-manja-mate ~]$
You'll need to remove this entry if you want to generate an ISO for Manjaro Mate.