hugolib: Fall back to title in ByLinkTitle sort

Fixes #4953

hugolib/page.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand"
 	"reflect"
 
 	"github.com/gohugoio/hugo/common/maps"
@@ -517,6 +518,14 @@ func (ps Pages) String() string {
 	return fmt.Sprintf("Pages(%d)", len(ps))
 }
 
+// Used in tests.
+func (ps Pages) shuffle() {
+	for i := range ps {
+		j := rand.Intn(i + 1)
+		ps[i], ps[j] = ps[j], ps[i]
+	}
+}
+
 func (ps Pages) findPagePosByFilename(filename string) int {
 	for i, x := range ps {
 		if x.Filename() == filename {