From 7af5dac2bb0d5938866ce6a92f040bee20fbb8a0 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Wed, 7 Mar 2018 11:41:23 +0100
Subject: [PATCH] fix crash when closing drawing view

---
 src/Gui/ViewProviderGroupExtension.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/Gui/ViewProviderGroupExtension.cpp b/src/Gui/ViewProviderGroupExtension.cpp
index f78084830d..8ac8961385 100644
--- a/src/Gui/ViewProviderGroupExtension.cpp
+++ b/src/Gui/ViewProviderGroupExtension.cpp
@@ -144,10 +144,14 @@ void ViewProviderGroupExtension::extensionHide(void) {
 
         const std::vector<App::DocumentObject*> & links = group->Group.getValues();
         Gui::Document* doc = Application::Instance->getDocument(getExtendedViewProvider()->getObject()->getDocument());
-        for (std::vector<App::DocumentObject*>::const_iterator it = links.begin(); it != links.end(); ++it) {
-            ViewProvider* view = doc->getViewProvider(*it);
-            if (view) 
-                view->hide();
+        // doc pointer can be null in case the document is about to be destroyed
+        // See https://forum.freecadweb.org/viewtopic.php?f=22&t=26797&p=218804#p218521
+        if (doc) {
+            for (std::vector<App::DocumentObject*>::const_iterator it = links.begin(); it != links.end(); ++it) {
+                ViewProvider* view = doc->getViewProvider(*it);
+                if (view)
+                    view->hide();
+            }
         }
     }