Regression in 0.23: msgfmt procedures invalid metainfo XML

After the update to gettext 0.23, the AppStream metainfo XML files generated by msgfmt are invalid if a translation is available for the ca@valencia language. The output from appstreamcli validate:

E: @appid@:79: tag-duplicated name (lang=ca)
   This tag must only appear once in this context. Having multiple tags of this kind is not valid.

E: @appid@:162: tag-duplicated summary (lang=ca)
   This tag must only appear once in this context. Having multiple tags of this kind is not valid.

Steps to reproduce:

git clone https://gitlab.gnome.org/GNOME/nautilus.git
msgfmt --xml --template nautilus/data/org.gnome.Nautilus.metainfo.xml.in.in -d nautilus/po -o org.gnome.Nautilus.metainfo.xml
appstreamcli validate --explain org.gnome.Nautilus.metainfo.xml

I'm reporting this issue here, because many GNOME applications use appstreamcli validate for test, and their builds now fail in check() due to this duplicated <name xml:lang="ca"> tag.