From b6b26b4e1ebaec13ae7baa83d459f17b2bbd8415 Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sat, 3 Aug 2019 17:14:56 -0600
Subject: [PATCH] Add some defensive code to prevent crash when no undo record
 is stacked.

Fixes: lp:1838843
* https://bugs.launchpad.net/kicad/+bug/1838843
---
 eeschema/schematic_undo_redo.cpp | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/eeschema/schematic_undo_redo.cpp b/eeschema/schematic_undo_redo.cpp
index d91ebfae29..34078534bd 100644
--- a/eeschema/schematic_undo_redo.cpp
+++ b/eeschema/schematic_undo_redo.cpp
@@ -362,14 +362,17 @@ void SCH_EDIT_FRAME::PutDataInPreviousState( PICKED_ITEMS_LIST* aList, bool aRed
 void SCH_EDIT_FRAME::RollbackSchematicFromUndo()
 {
     PICKED_ITEMS_LIST* undo = GetScreen()->PopCommandFromUndoList();
-    PutDataInPreviousState( undo, false );
 
-    undo->ClearListAndDeleteItems();
-    delete undo;
+    if( undo )
+    {
+        PutDataInPreviousState( undo, false );
+        undo->ClearListAndDeleteItems();
+        delete undo;
 
-    SetSheetNumberAndCount();
+        SetSheetNumberAndCount();
 
-    TestDanglingEnds();
+        TestDanglingEnds();
+    }
 
     SyncView();
     GetCanvas()->Refresh();