From 8a21cd4daa8cb705a42030bf8b7ac2f340a154c7 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Sat, 8 Oct 2016 12:47:27 +0200
Subject: [PATCH] fix crash in DocumentIndex::cloneViewProvider

---
 src/Gui/DocumentModel.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Gui/DocumentModel.cpp b/src/Gui/DocumentModel.cpp
index 48cc92c8a3..7b3420b146 100644
--- a/src/Gui/DocumentModel.cpp
+++ b/src/Gui/DocumentModel.cpp
@@ -225,8 +225,11 @@ namespace Gui {
         it = vp_nodes.find(&vp);
         if (it != vp_nodes.end()) {
             boost::unordered_set<ViewProviderIndex*>::const_iterator v;
-            v = it->second.begin();
-            return (*v)->clone();
+            if (!it->second.empty()) {
+                v = it->second.begin();
+                if (*v)
+                    return (*v)->clone();
+            }
         }
         return new ViewProviderIndex(vp, const_cast<DocumentIndex*>(this));
     }