Spreadsheet: Fixed bug with dangling pointer when a document object is deleted.

src/Mod/Spreadsheet/App/PropertySheet.cpp

@@ -1089,6 +1089,11 @@ void PropertySheet::renamedDocument(const App::Document * doc)
     }
 }
 
+void PropertySheet::deletedDocumentObject(const App::DocumentObject *docObj)
+{
+    docDeps.erase(const_cast<App::DocumentObject*>(docObj));
+}
+
 void PropertySheet::documentSet()
 {
     documentName[owner->getDocument()] = owner->getDocument()->Label.getValue();

src/Mod/Spreadsheet/App/PropertySheet.h

@@ -143,6 +143,8 @@ public:
 
     void renamedDocument(const App::Document *doc);
 
+    void deletedDocumentObject(const App::DocumentObject *docObj);
+
     void documentSet();
 
 private:

src/Mod/Spreadsheet/App/SheetObserver.cpp

@@ -60,6 +60,7 @@ void SheetObserver::slotCreatedObject(const DocumentObject &Obj)
 void SheetObserver::slotDeletedObject(const DocumentObject &Obj)
 {
     sheet->invalidateDependants(&Obj);
+    sheet->deletedDocumentObject(&Obj);
 }
 
 /**