From 84903d05c2846014fda650921e5f948ea60774cb Mon Sep 17 00:00:00 2001
From: Richard Roberts <richard.jw.roberts@gmail.com>
Date: Tue, 4 Jun 2013 17:34:03 +0000
Subject: [PATCH] Fixed iSAM2 bug where assignment operator and copy
 constructor may cause null pointer exception when trying to clone cached
 linear factors, which become null by calling marginalizeLeaves with linear
 factor caching enabled.

---
 gtsam/nonlinear/ISAM2.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gtsam/nonlinear/ISAM2.cpp b/gtsam/nonlinear/ISAM2.cpp
index 9b063f0ce..a209c3d44 100644
--- a/gtsam/nonlinear/ISAM2.cpp
+++ b/gtsam/nonlinear/ISAM2.cpp
@@ -125,7 +125,7 @@ ISAM2& ISAM2::operator=(const ISAM2& rhs) {
   linearFactors_ = GaussianFactorGraph();
   linearFactors_.reserve(rhs.linearFactors_.size());
   BOOST_FOREACH(const GaussianFactor::shared_ptr& linearFactor, rhs.linearFactors_) {
-    linearFactors_.push_back(linearFactor->clone()); }
+    linearFactors_.push_back(linearFactor ? linearFactor->clone() : GaussianFactor::shared_ptr()); }
 
   ordering_ = rhs.ordering_;
   params_ = rhs.params_;