From 4929827f70947eaca85371b246e4ad14346b058f Mon Sep 17 00:00:00 2001
From: ShuangLiu1992 <ShuangLiu1992@users.noreply.github.com>
Date: Fri, 27 Jan 2023 16:43:27 +0000
Subject: [PATCH] fix SmartFactorBase as well

---
 gtsam/slam/SmartFactorBase.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gtsam/slam/SmartFactorBase.h b/gtsam/slam/SmartFactorBase.h
index 80dde3563..e0540cc41 100644
--- a/gtsam/slam/SmartFactorBase.h
+++ b/gtsam/slam/SmartFactorBase.h
@@ -243,7 +243,7 @@ protected:
    * to the matrices and vectors that will be used to store the results instead
    * of pointers.
    */
-  template<class POINT, class ...OptArgs>
+  template<class POINT, class ...OptArgs, typename = std::enable_if_t<sizeof...(OptArgs)!=0>>
   Vector unwhitenedError(
       const Cameras& cameras, const POINT& point,
       OptArgs&&... optArgs) const {