From d562587858d21899642831df9bce5b660ecdcc06 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 12 Jul 2019 17:00:20 +0100
Subject: [PATCH] Added check against any empty _segments to avoid undefined
 behaviour

---
 src/osgSim/ElevationSlice.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/osgSim/ElevationSlice.cpp b/src/osgSim/ElevationSlice.cpp
index bdc4f193a..ce035742e 100644
--- a/src/osgSim/ElevationSlice.cpp
+++ b/src/osgSim/ElevationSlice.cpp
@@ -1092,6 +1092,8 @@ struct LineConstructor
 
     void copyPoints(ElevationSlice::Vec3dList& intersections, ElevationSlice::DistanceHeightList& distanceHeightIntersections)
     {
+        if (_segments.empty()) return;
+
         SegmentSet::iterator prevItr = _segments.begin();
         SegmentSet::iterator nextItr = prevItr;
         ++nextItr;