From dd9596969534f5f5f4ca477568d7f3e4bcee66c7 Mon Sep 17 00:00:00 2001
From: wandererfan <wandererfan@gmail.com>
Date: Sat, 27 Aug 2022 10:35:14 -0400
Subject: [PATCH] [TD]fix crash in Preferences

- QGVPage was not detaching the parameter observer when
  deleted, leaving a stale pointer in the list of observers.
---
 src/Mod/TechDraw/Gui/QGVPage.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Mod/TechDraw/Gui/QGVPage.cpp b/src/Mod/TechDraw/Gui/QGVPage.cpp
index 97212bc769..4d3efd7d6e 100644
--- a/src/Mod/TechDraw/Gui/QGVPage.cpp
+++ b/src/Mod/TechDraw/Gui/QGVPage.cpp
@@ -225,6 +225,11 @@ public:
             }
         }
     }
+    void detach() {
+        hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/View");
+        hGrp->Detach(this);
+
+    }
 };
 
 QGVPage::QGVPage(ViewProviderPage *vp, QGSPage* s, QWidget *parent)
@@ -285,6 +290,7 @@ QGVPage::~QGVPage()
 {
     delete bkgBrush;
     delete m_navStyle;
+    d->detach();
 }
 
 void QGVPage::centerOnPage(void)