fix(list): return lists for a namespace id even if that namespace is deleted

This fixes a problem where a namespace was deleted and its list were not.
Forum discussion: https://community.vikunja.io/t/list-deleted-but-tasks-showing-up-as-archived-and-overdue/1025

pkg/models/list.go

@@ -156,7 +156,7 @@ func GetListsByNamespaceID(s *xorm.Session, nID int64, doer *user.User) (lists [
 			Alias("l").
 			Join("LEFT", []string{"namespaces", "n"}, "l.namespace_id = n.id").
 			Where("l.is_archived = false").
-			Where("n.is_archived = false").
+			Where("n.is_archived = false OR n.is_archived IS NULL").
 			Where("namespace_id = ?", nID).
 			Find(&lists)
 	}