Comment 0 for bug 1624661

When data folder was moved from E: to D:, the following traceback
appears on startup after a few "Missing DB messages.

Trunk 2696 | Win 10

Traceback (most recent call last):
  File "openlp.py", line 44, in <module>
    main()
  File "D:\bzr\openlp\trunk\openlp\core\__init__.py", line 392, in main
    sys.exit(application.run(qt_args))
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 59, in wrapped
    raise e
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "D:\bzr\openlp\trunk\openlp\core\__init__.py", line 142, in run
    Registry().execute('bootstrap_initialise')
  File "D:\bzr\openlp\trunk\openlp\core\common\registry.py", line 137, in execute
    result = function(*args, **kwargs)
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 59, in wrapped
    raise e
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "D:\bzr\openlp\trunk\openlp\core\lib\pluginmanager.py", line 59, in bootstrap_initialise
    self.hook_media_manager()
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 59, in wrapped
    raise e
  File "D:\bzr\openlp\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "D:\bzr\openlp\trunk\openlp\core\lib\pluginmanager.py", line 123, in hook_media_manager
    plugin.create_media_manager_item()
  File "D:\bzr\openlp\trunk\openlp\core\lib\plugin.py", line 203, in create_media_manager_item
    self.media_item = self.media_item_class(self.main_window.media_dock_manager.media_dock, self)
  File "D:\bzr\openlp\trunk\openlp\plugins\images\lib\mediaitem.py", line 55, in __init__
    super(ImageMediaItem, self).__init__(parent, plugin)
  File "D:\bzr\openlp\trunk\openlp\core\lib\mediamanageritem.py", line 83, in __init__
    self.setup_item()
  File "D:\bzr\openlp\trunk\openlp\plugins\images\lib\mediaitem.py", line 68, in setup_item
    self.fill_groups_combobox(self.choose_group_form.group_combobox)
  File "D:\bzr\openlp\trunk\openlp\plugins\images\lib\mediaitem.py", line 300, in fill_groups_combobox
    image_groups = self.manager.get_all_objects(ImageGroups, ImageGroups.parent_id == parent_group_id)
  File "D:\bzr\openlp\trunk\openlp\core\lib\db.py", line 368, in get_all_objects
    query = self.session.query(object_class)
AttributeError: 'NoneType' object has no attribute 'query'