From daeaa2b7e39f2ed94a91cf0a4f6acbdfffbbfa8f Mon Sep 17 00:00:00 2001
From: wandererfan <wandererfan@gmail.com>
Date: Thu, 28 Dec 2023 09:40:41 -0500
Subject: [PATCH] [TD]fix fail when dropping onto corrupt object

---
 .../Gui/ViewProviderDrawingViewExtension.cpp    | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/Mod/TechDraw/Gui/ViewProviderDrawingViewExtension.cpp b/src/Mod/TechDraw/Gui/ViewProviderDrawingViewExtension.cpp
index 991ca34d12..18112b968f 100644
--- a/src/Mod/TechDraw/Gui/ViewProviderDrawingViewExtension.cpp
+++ b/src/Mod/TechDraw/Gui/ViewProviderDrawingViewExtension.cpp
@@ -58,9 +58,24 @@ void ViewProviderDrawingViewExtension::extensionDragObject(App::DocumentObject*
 //extension to try to drop on us and cause problems
 bool ViewProviderDrawingViewExtension::extensionCanDropObjects() const { return true; }
 
-//let the page have any drops we receive
+//let the page have any drops we receive.
 bool ViewProviderDrawingViewExtension::extensionCanDropObject(App::DocumentObject* obj) const
 {
+    // it can happen that if the tree gets badly corrupted, there can be loose
+    // objects that have no page or view provider, so we need to check that
+    // all these objects exist.
+    auto vpdv = getViewProviderDrawingView();
+    if (!vpdv) {
+        return false;
+    }
+    auto vpp  = vpdv->getViewProviderPage();
+    if (!vpp) {
+        return false;
+    }
+    auto vppEx = vpp->getVPPExtension();
+    if (!vppEx) {
+        return false;
+    }
     return getViewProviderDrawingView()
         ->getViewProviderPage()
         ->getVPPExtension()