Possible solution to set the correct version in the PDF footer

[thrashwerk]

Related to !835.

Tested locally and in GH Actions on my fork.

[thrashwerk]

My mistake, / is not a safe separator for sed in this case.

GITHUB_REF_NAME most likely was thrashwerk/pdf-footer-version so the sed instruction became s/%%FOOTER_VERSION%%/thrashwerk/pdf-footer-version/ which obviously isn't right.

Maybe | wouldn't cause any more conflicts.
For example

if [ -v GITHUB_REF_NAME ]; then
    sed "s|%%FOOTER_VERSION%%|${GITHUB_REF_NAME}|" meta.tmpl.tex > meta.tex
else
    sed "s|%%FOOTER_VERSION%%|UNDEFINED VERSION|" meta.tmpl.tex > meta.tex
fi