From aabe2d6cda9a24be85fa88146c6bb2b81bafd29e Mon Sep 17 00:00:00 2001
From: azv <azv@opencascade.com>
Date: Mon, 31 Oct 2016 10:34:54 +0300
Subject: [PATCH] Fix crash when removing point under Middle and Coincidence
 constraints (issues #1762, #1769)

---
 src/SketchSolver/SketchSolver_ConstraintMiddle.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/SketchSolver/SketchSolver_ConstraintMiddle.cpp b/src/SketchSolver/SketchSolver_ConstraintMiddle.cpp
index 545fa4687..362bc58cc 100644
--- a/src/SketchSolver/SketchSolver_ConstraintMiddle.cpp
+++ b/src/SketchSolver/SketchSolver_ConstraintMiddle.cpp
@@ -32,6 +32,12 @@ void SketchSolver_ConstraintMiddle::notifyCoincidenceChanged(
   for (int i = 0; i < 2 && isSameAttr; ++i) {
     AttributeRefAttrPtr aRefAttr = std::dynamic_pointer_cast<ModelAPI_AttributeRefAttr>(
         myBaseConstraint->attribute(SketchPlugin_Constraint::ATTRIBUTE(i)));
+    if (!aRefAttr)
+    {
+      // It seems the Middle point constraint has been deleted, so keep it unchanged.
+      // It will be removed later.
+      return;
+    }
     if (aRefAttr->isObject()) {
       FeaturePtr aFeature = ModelAPI_Feature::feature(aRefAttr->object());
       isSameAttr = (aFeature == aLine);
-- 
2.39.2