[libdazzle] tree-node: set the dummy bit

[Christian Hergert <chergert src gnome org>]

commit 6df5b44e795390404c6fdc08eb90583130dd88b6
Author: Christian Hergert <chergert redhat com>
Date:   Mon Dec 4 17:50:55 2017 -0800

    tree-node: set the dummy bit
    
    This should have been set, but seems to have been lost in some
    previous iteration.

 src/tree/dzl-tree-node.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/tree/dzl-tree-node.c b/src/tree/dzl-tree-node.c
index 92d6ef9..cf62721 100644
--- a/src/tree/dzl-tree-node.c
+++ b/src/tree/dzl-tree-node.c
@@ -1081,6 +1081,7 @@ _dzl_tree_node_add_dummy_child (DzlTreeNode *self)
   dummy = g_object_ref_sink (dzl_tree_node_new ());
   _dzl_tree_node_set_tree (dummy, self->tree);
   _dzl_tree_node_set_parent (dummy, self);
+  dummy->is_dummy = TRUE;
   gtk_tree_store_insert_with_values (model, &iter, &parent, -1,
                                      0, dummy,
                                      -1);