Traceback when going from blanked presentation to video

First reported on the forum: http://forums.openlp.org/discussion/2633/crash-moving-from-powerpoint-to-video-with-screen-blanked

Confirmed with 2.1.5 on windows 8.1, vlc, though not reproduceable on all setups.

Traceback when going from blanked (black) presentation to video:

Traceback (most recent call last):
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\servicemanager.py", line 1462, in on_make_live
    self.make_live()
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\servicemanager.py", line 1478, in make_live
    self.live_controller.add_service_manager_item(self.service_items[item]['service_item'], child)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\slidecontroller.py", line 808, in add_service_manager_item
    self._process_item(item, slide_num)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\slidecontroller.py", line 834, in _process_item
    self._reset_blank(self.service_item.is_capable(ItemCapabilities.ProvidesOwnDisplay))
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\slidecontroller.py", line 1381, in _reset_blank
    self.on_blank_display(True)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\slidecontroller.py", line 975, in on_blank_display
    self.blank_plugin()
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\slidecontroller.py", line 1032, in blank_plugin
    self.service_item.name.lower(), [self.service_item, self.is_live, hide_mode])
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\registry.py", line 137, in execute
    result = function(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 58, in wrapped
    raise e
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\common\openlpmixin.py", line 54, in wrapped
    return func(*args, **kwargs)
  File "C:\Users\tgc\OpenLP\trunk\openlp\core\ui\media\mediacontroller.py", line 740, in media_blank
    if self.current_media_players[self.live_controller.controller_type].state == MediaState.Playing:
KeyError: 0