Fixed destructors of DiffViewCtrl and ObjectList after 8342b7f95b and 0726b46da2.

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -239,7 +239,8 @@ ObjectList::ObjectList(wxWindow* parent) :
 
 ObjectList::~ObjectList()
 {
-    delete m_objects_model;
+    if (m_objects_model)
+        m_objects_model->DecRef();
 }
 
 void ObjectList::set_min_height()

src/slic3r/GUI/UnsavedChangesDialog.hpp

@@ -204,7 +204,12 @@ class DiffViewCtrl : public wxDataViewCtrl
 
 public:
     DiffViewCtrl(wxWindow* parent, wxSize size);
-    ~DiffViewCtrl() override { Clear(); delete model; }
+    ~DiffViewCtrl() override {
+        if (model) {
+            Clear();
+            model->DecRef();
+        }
+    }
 
     DiffModel* model{ nullptr };