base_print.html doesn't uses correct site preferences if run in background

As the preferences are accessed trough request.site and there is no request if the PDF generation is run in background, the preferences are not used.

added part::backend part::frontend prio::1 source::customer type::bug labels

assigned to @hansegucker

created merge request !777 (merged) to address this issue

mentioned in merge request !777 (merged)

closed with merge request !777 (merged)

mentioned in commit cc58bc0b