From 39b81e40a93bd1c55a89d6cf2e2710b8be68546b Mon Sep 17 00:00:00 2001
From: Abdullah Tahiri <abdullah.tahiri.yo@gmail.com>
Date: Tue, 7 Jul 2020 18:09:55 +0200
Subject: [PATCH] Sketcher: fix access to isPerformingTransaction on null
 pointer

===============================================================

Fixes this crash:
https://forum.freecadweb.org/viewtopic.php?f=3&t=48414#p414255
---
 src/Mod/Sketcher/App/SketchObject.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Mod/Sketcher/App/SketchObject.cpp b/src/Mod/Sketcher/App/SketchObject.cpp
index 038847366d..ea390ada3f 100644
--- a/src/Mod/Sketcher/App/SketchObject.cpp
+++ b/src/Mod/Sketcher/App/SketchObject.cpp
@@ -7040,7 +7040,9 @@ void SketchObject::onChanged(const App::Property* prop)
 
     if (prop == &Geometry || prop == &Constraints) {
 
-        if(getDocument()->isPerformingTransaction()) { // undo/redo
+        auto doc = getDocument();
+
+        if(doc && doc->isPerformingTransaction()) { // undo/redo
             setStatus(App::PendingTransactionUpdate, true);
         }
         else {