If a label was created by a prolog rule and approved by it, the
Polygerrit UI still showed the notice "No Votes" in addition to the
thumbs up vote, which was automatically created by the prolog rule.
The placeholder will now also be hidden, if the LabelInfo-object does
not have a values-field, but was either accepted or rejected, which
will be the case, if the label was created and voted on by a prolog
rule.
Issue: 12777
Change-Id: Ic776a48ab03e7eb0993ea1fdcbc682ea64638c04