The templatetag was created during a cleanup of the previous 'partner' logic,
which did not assume a partner to be present. Adapt the new logic to also not
assume that.
This one was tricky as the templatetag is loaded as part of the base-template,
which again is loaded by the 404-template, which is loaded e.g. if there is
no matching organisation for the query. The fact that the templatetag did not
handle this let to a 500-error within the 404-error.