Slightly generalized the crash fix in revision 54111.

Also added a warning message to anticipate potential issues due to
the implication of the problem addressed here.

2 files changed, 12 insertions, 6 deletions

diff --git a/source/blender/freestyle/intern/view_map/FEdgeXDetector.cpp b/source/blender/freestyle/intern/view_map/FEdgeXDetector.cpp
index 9631c93cd7e..2ded242e9ea 100644
--- a/source/blender/freestyle/intern/view_map/FEdgeXDetector.cpp
+++ b/source/blender/freestyle/intern/view_map/FEdgeXDetector.cpp
@@ -40,6 +40,8 @@
 #include "../geometry/GeomUtils.h"
 #include "../geometry/normal_cycle.h"
 
+#include "BKE_global.h"
+
 void FEdgeXDetector::processShapes(WingedEdge& we)
 {
 	bool progressBarDisplay = false;
@@ -171,6 +173,16 @@ void FEdgeXDetector::preProcessFace(WXFace *iFace)
 
 void FEdgeXDetector::computeCurvatures(WXVertex *vertex)
 {
+	// TODO: for some reason, the 'vertex' may have no associated edges
+	// (i.e., WVertex::_EdgeList is empty), which causes a crash due to
+	// a subsequent call of WVertex::_EdgeList.front().
+	if (vertex->GetEdges().empty()) {
+		if (G.debug & G_DEBUG_FREESTYLE) {
+			printf("Warning: WVertex %d has no associated edges.\n", vertex->GetId());
+		}
+		return;
+	}
+
 	// CURVATURE LAYER
 	// store all the curvature datas for each vertex
 
diff --git a/source/blender/freestyle/intern/winged_edge/Curvature.cpp b/source/blender/freestyle/intern/winged_edge/Curvature.cpp
index 65ebdeac3a8..64b897c5596 100644
--- a/source/blender/freestyle/intern/winged_edge/Curvature.cpp
+++ b/source/blender/freestyle/intern/winged_edge/Curvature.cpp
@@ -586,12 +586,6 @@ static bool sphere_clip_vector(const Vec3r& O, real r, const Vec3r& P, Vec3r& V)
 // use marking ? (measure *timings* ...)
 void compute_curvature_tensor(WVertex *start, real radius, NormalCycle& nc)
 {
-	// TODO: for some reason, the WVertex 'start' may have no associated edges
-	// (i.e., WVertex::_EdgeList is empty), which causes a crash due to a call
-	// of WVertex::_EdgeList.front().
-	if (start->GetEdges().empty())
-		return;
-
 	// in case we have a non-manifold vertex, skip it...
 	if (start->isBoundary())
 		return;