AttributeError: 'CommitDialog' object has no attribute '_last_selected_file'

I occasionally see the following traceback when committing use bzr-gtk r769 on precise:

  File "/home/curtis/.bazaar/plugins/gtk/commit.py", line 579, in _on_treeview_files_cursor_changed
    self._update_per_file_info(selection)
  File "/home/curtis/.bazaar/plugins/gtk/commit.py", line 618, in _update_per_file_info
    self._save_current_file_message()
  File "/home/curtis/.bazaar/plugins/gtk/commit.py", line 605, in _save_current_file_message
    if self._last_selected_file is None:
AttributeError: 'CommitDialog' object has no attribute '_last_selected_file'

The commit is successful. Looking at the order of events,
_construct_file_list() connects _on_treeview_files_cursor_changed() to the cursor-changed signal.
_on_treeview_files_cursor_changed() presumes _last_selected_file() was created,
but it will not be created until _fill_in_per_file_info() is called (which is two lines before _construct_file_list())

The cursor-changed signal may have been called after _fill_in_per_file_info(), but it is often called before with
Gtk3.