[glom/gtkmm4v4] gtkmm4: Avoid creating RefPtr to this.

[Murray Cumming <murrayc src gnome org>]

commit 4e82a244ae6ba2a9e7e962b3f83c092f7084234f
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Apr 15 16:30:00 2017 +0200

    gtkmm4: Avoid creating RefPtr to this.

 glom/mode_data/datawidget/treemodel_db.cc |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)
---
diff --git a/glom/mode_data/datawidget/treemodel_db.cc b/glom/mode_data/datawidget/treemodel_db.cc
index b5d0e45..49ba823 100644
--- a/glom/mode_data/datawidget/treemodel_db.cc
+++ b/glom/mode_data/datawidget/treemodel_db.cc
@@ -657,10 +657,7 @@ Gtk::TreeModel::Path DbTreeModel::get_path_vfunc(const const_iterator& iter) con
 
 bool DbTreeModel::create_iterator(const type_datamodel_row_index& datamodel_row, DbTreeModel::iterator& 
iter) const
 {
-  Glib::RefPtr<DbTreeModel> refModel(const_cast<DbTreeModel*>(this));
-  refModel->reference();
-
-  iter.set_model_refptr(refModel);
+  iter.set_model_gobject(const_cast<GtkTreeModel*>(gobj()));
 
   const guint count_all_rows = std::max(0, get_internal_rows_count());
   //g_warning("DbTreeModel::create_iterator(): datamodel_row=%d, count=%d", datamodel_row, count_all_rows);