[gtk+] gtk-demo: Make editable cells demo more robust

[Matthias Clasen <matthiasc src gnome org>]

commit 531fa7860135cd339475d5411dd8630313990e91
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Jan 19 07:32:31 2015 -0500

    gtk-demo: Make editable cells demo more robust
    
    When removing all rows, trying to add rows would not work
    and throw criticals. This is fallout from a recent change
    to insert rows at the right position. Fix this by handling
    the 'empty model' case separately.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743157

 demos/gtk-demo/editable_cells.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)
---
diff --git a/demos/gtk-demo/editable_cells.c b/demos/gtk-demo/editable_cells.c
index 18ff477..717bf50 100644
--- a/demos/gtk-demo/editable_cells.c
+++ b/demos/gtk-demo/editable_cells.c
@@ -158,11 +158,18 @@ add_item (GtkWidget *button, gpointer data)
   /* Insert a new row below the current one */
   gtk_tree_view_get_cursor (treeview, &path, NULL);
   model = gtk_tree_view_get_model (treeview);
-  gtk_tree_model_get_iter (model, &current, path);
-  gtk_tree_path_free (path);
+  if (path)
+    {
+      gtk_tree_model_get_iter (model, &current, path);
+      gtk_tree_path_free (path);
+      gtk_list_store_insert_after (GTK_LIST_STORE (model), &iter, &current);
+    }
+  else
+    {
+      gtk_list_store_insert (GTK_LIST_STORE (model), &iter, -1);
+    }
 
   /* Set the data for the new row */
-  gtk_list_store_insert_after (GTK_LIST_STORE (model), &iter, &current);
   gtk_list_store_set (GTK_LIST_STORE (model), &iter,
                       COLUMN_ITEM_NUMBER, foo.number,
                       COLUMN_ITEM_PRODUCT, foo.product,