From 62dee011efaeedc1fec3742460203a9adcfa06d3 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Tue, 5 Mar 2024 10:19:07 +0100
Subject: [PATCH] Sketcher: fix crash when trying to edit malformed sketch

For more details see: https://forum.freecad.org/viewtopic.php?p=745031#p745031
---
 src/Mod/Sketcher/Gui/EditModeConstraintCoinManager.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/Mod/Sketcher/Gui/EditModeConstraintCoinManager.cpp b/src/Mod/Sketcher/Gui/EditModeConstraintCoinManager.cpp
index 0af1df62e6..04fc7cdaa8 100644
--- a/src/Mod/Sketcher/Gui/EditModeConstraintCoinManager.cpp
+++ b/src/Mod/Sketcher/Gui/EditModeConstraintCoinManager.cpp
@@ -1749,9 +1749,11 @@ void EditModeConstraintCoinManager::updateConstraintColor(
 
         SoMaterial* m = nullptr;
         if (!hasDatumLabel && type != Sketcher::Coincident && type != Sketcher::InternalAlignment) {
-            hasMaterial = true;
-            m = static_cast<SoMaterial*>(
-                s->getChild(static_cast<int>(ConstraintNodePosition::MaterialIndex)));
+            int matIndex = static_cast<int>(ConstraintNodePosition::MaterialIndex);
+            if (matIndex < s->getNumChildren()) {
+                hasMaterial = true;
+                m = static_cast<SoMaterial*>(s->getChild(matIndex));
+            }
         }
 
         auto selectpoint = [this, pcolor, PtNum](int geoid, Sketcher::PointPos pos) {