[gnome-builder] project-tree: hold a reference during destroy operations

[Christian Hergert <chergert src gnome org>]

commit c7dfcda9c59807248c6e2576d932aa658e2c38f5
Author: Christian Hergert <christian hergert me>
Date:   Mon May 11 16:08:19 2015 -0700

    project-tree: hold a reference during destroy operations
    
    Better safe than assert.

 src/project-tree/gb-project-tree-actions.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/project-tree/gb-project-tree-actions.c b/src/project-tree/gb-project-tree-actions.c
index 4c5b730..ec0b2a7 100644
--- a/src/project-tree/gb-project-tree-actions.c
+++ b/src/project-tree/gb-project-tree-actions.c
@@ -922,10 +922,11 @@ gb_project_tree_actions_move_to_trash (GSimpleAction *action,
    */
   ifile = ide_project_get_project_file (project, file);
   buffer = ide_buffer_manager_find_buffer (buffer_manager, ifile);
-  removal.document = GB_DOCUMENT (buffer);
+  removal.document = g_object_ref (buffer);
   gb_workbench_views_foreach (workbench,
                               gb_project_tree_actions_close_views_cb,
                               &removal);
+  g_object_unref (removal.document);
 
   /*
    * Close all of the views that match the document.