YouTube reverted the changes they made that prompted f9f5d5ba.
In case they change their minds again, this adds support for both
formats.
The liberal_update and conservative_update functions needed to be
modified to handle the cases of empty lists, so that
a successfully extracted 'music_list': [{'Author':...},...] will
not be overwritten by 'music_list': [] in the calls to
liberal_dict_update.
Signed-off-by: Jesús <heckyel@hyperbola.info>
2039972ab3