Don't fail when calling Paginate with an empty pages.PagesGroup

Fixes #10802

resources/page/pagegroup.go

@@ -430,14 +430,14 @@ func (psg PagesGroup) ProbablyEq(other any) bool {
 }
 
 // ToPagesGroup tries to convert seq into a PagesGroup.
-func ToPagesGroup(seq any) (PagesGroup, error) {
+func ToPagesGroup(seq any) (PagesGroup, bool, error) {
 	switch v := seq.(type) {
 	case nil:
-		return nil, nil
+		return nil, true, nil
 	case PagesGroup:
-		return v, nil
+		return v, true, nil
 	case []PageGroup:
-		return PagesGroup(v), nil
+		return PagesGroup(v), true, nil
 	case []any:
 		l := len(v)
 		if l == 0 {
@@ -450,12 +450,12 @@ func ToPagesGroup(seq any) (PagesGroup, error) {
 				if pg, ok := ipg.(PageGroup); ok {
 					pagesGroup[i] = pg
 				} else {
-					return nil, fmt.Errorf("unsupported type in paginate from slice, got %T instead of PageGroup", ipg)
+					return nil, false, fmt.Errorf("unsupported type in paginate from slice, got %T instead of PageGroup", ipg)
 				}
 			}
-			return pagesGroup, nil
+			return pagesGroup, true, nil
 		}
 	}
 
-	return nil, nil
+	return nil, false, nil
 }

resources/page/pagination.go

@@ -277,11 +277,11 @@ func Paginate(td TargetPathDescriptor, seq any, pagerSize int) (*Paginator, erro
 
 	var paginator *Paginator
 
-	groups, err := ToPagesGroup(seq)
+	groups, ok, err := ToPagesGroup(seq)
 	if err != nil {
 		return nil, err
 	}
-	if groups != nil {
+	if ok {
 		paginator, _ = newPaginatorFromPageGroups(groups, pagerSize, urlFactory)
 	} else {
 		pages, err := ToPages(seq)