173: Invalid @footer value
The footer
metadata name is declared to turn the automatic integration of a @footer.nml file off or to link a footer file manually. However, the assigned value is neither off
nor a link in your case.
Solution
Assign the value off
to turn the automatic integration of a @footer.nml file off:
@ footer: off
Use an arrow before the filepath, if you want to point to a footer file manually:
@ header: ->/my/sitelinks.nml