staticcheck reports

    ziobtree.go:606:4: Errorf is a pure function but its return value is ignored (SA4017)
    ziobtree.go:626:4: Errorf is a pure function but its return value is ignored (SA4017)
    zlobtree.go:606:4: Errorf is a pure function but its return value is ignored (SA4017)
    zlobtree.go:626:4: Errorf is a pure function but its return value is ignored (SA4017)