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