From 5b5243eae542a6fbc4a10de0fd7193597060cfb3 Mon Sep 17 00:00:00 2001
From: WandererFan <wandererfan@gmail.com>
Date: Sun, 3 Jul 2016 20:23:08 -0400
Subject: [PATCH] prevent fail when scale is zero

---
 src/Mod/TechDraw/App/DrawViewPart.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Mod/TechDraw/App/DrawViewPart.cpp b/src/Mod/TechDraw/App/DrawViewPart.cpp
index b0be5e0320..c75fe1b6c3 100644
--- a/src/Mod/TechDraw/App/DrawViewPart.cpp
+++ b/src/Mod/TechDraw/App/DrawViewPart.cpp
@@ -367,10 +367,14 @@ void DrawViewPart::extractFaces()
     }
 
     std::vector<TopoDS_Wire> sortedWires = sortWiresBySize(fw,false);
+    if (!sortedWires.size()) {
+        Base::Console().Log("INFO - DVP::extractFaces - no sorted Wires!\n");
+        return;                                     // might happen in the middle of changes?
+    }
 
     //remove the largest wire (OuterWire of graph)
     Bnd_Box bigBox;
-    if (!(sortedWires.back().IsNull())) {
+    if (sortedWires.size() && !sortedWires.front().IsNull()) {
         BRepBndLib::Add(sortedWires.front(), bigBox);
         bigBox.SetGap(0.0);
     }