[gtk+/gtk-3-20] treeview: Fix a rubberbanding-related crash

[Matthias Clasen <matthiasc src gnome org>]

commit a2d723c13391e560cce7e5aed62554114f346c83
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu May 19 16:59:10 2016 -0400

    treeview: Fix a rubberbanding-related crash
    
    When starting a rubberband selection from an empty area, we could run
    into crashes if the selection moves over the rows and then back out
    to unpopulated area. Handle this case without crashing.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766336

 gtk/gtktreeview.c |   55 +++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 41 insertions(+), 14 deletions(-)
---
diff --git a/gtk/gtktreeview.c b/gtk/gtktreeview.c
index f6f0c1c..a72750c 100644
--- a/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@ -4381,24 +4381,30 @@ gtk_tree_view_stop_rubber_band (GtkTreeView *tree_view)
       gtk_widget_queue_draw (GTK_WIDGET (tree_view));
 
       /* The anchor path should be set to the start path */
-      tmp_path = _gtk_tree_path_new_from_rbtree (tree_view->priv->rubber_band_start_tree,
-                                                tree_view->priv->rubber_band_start_node);
+      if (tree_view->priv->rubber_band_start_node)
+        {
+          tmp_path = _gtk_tree_path_new_from_rbtree (tree_view->priv->rubber_band_start_tree,
+                                                     tree_view->priv->rubber_band_start_node);
 
-      if (tree_view->priv->anchor)
-       gtk_tree_row_reference_free (tree_view->priv->anchor);
+          if (tree_view->priv->anchor)
+            gtk_tree_row_reference_free (tree_view->priv->anchor);
 
-      tree_view->priv->anchor =
-       gtk_tree_row_reference_new_proxy (G_OBJECT (tree_view),
-                                         tree_view->priv->model,
-                                         tmp_path);
+          tree_view->priv->anchor =
+            gtk_tree_row_reference_new_proxy (G_OBJECT (tree_view),
+                                              tree_view->priv->model,
+                                              tmp_path);
 
-      gtk_tree_path_free (tmp_path);
+          gtk_tree_path_free (tmp_path);
+        }
 
       /* ... and the cursor to the end path */
-      tmp_path = _gtk_tree_path_new_from_rbtree (tree_view->priv->rubber_band_end_tree,
-                                                 tree_view->priv->rubber_band_end_node);
-      gtk_tree_view_real_set_cursor (GTK_TREE_VIEW (tree_view), tmp_path, 0);
-      gtk_tree_path_free (tmp_path);
+      if (tree_view->priv->rubber_band_end_node)
+        {
+          tmp_path = _gtk_tree_path_new_from_rbtree (tree_view->priv->rubber_band_end_tree,
+                                                     tree_view->priv->rubber_band_end_node);
+          gtk_tree_view_real_set_cursor (GTK_TREE_VIEW (tree_view), tmp_path, 0);
+          gtk_tree_path_free (tmp_path);
+        }
 
       _gtk_tree_selection_emit_changed (tree_view->priv->selection);
 
@@ -4535,7 +4541,28 @@ gtk_tree_view_update_rubber_band_selection (GtkTreeView *tree_view)
   _gtk_rbtree_find_offset (tree_view->priv->tree, MAX (tree_view->priv->press_start_y, bin_y), &end_tree, 
&end_node);
 
   /* Handle the start area first */
-  if (!tree_view->priv->rubber_band_start_node)
+  if (!start_node && !end_node)
+    {
+      if (tree_view->priv->rubber_band_start_node)
+        {
+          GtkRBNode *node = tree_view->priv->rubber_band_start_node;
+          GtkRBTree *tree = tree_view->priv->rubber_band_start_tree;
+
+         if (tree_view->priv->rubber_band_modify)
+           {
+             /* Toggle the selection state */
+             if (GTK_RBNODE_FLAG_SET (node, GTK_RBNODE_IS_SELECTED))
+               GTK_RBNODE_UNSET_FLAG (node, GTK_RBNODE_IS_SELECTED);
+             else
+               GTK_RBNODE_SET_FLAG (node, GTK_RBNODE_IS_SELECTED);
+           }
+          else
+            GTK_RBNODE_UNSET_FLAG (node, GTK_RBNODE_IS_SELECTED);
+
+          _gtk_tree_view_queue_draw_node (tree_view, tree, node, NULL);
+        }
+    }
+  if (!tree_view->priv->rubber_band_start_node || !start_node)
     {
       gtk_tree_view_update_rubber_band_selection_range (tree_view,
                                                       start_tree,