Improvments to tvdb and eztv scrapper

fixed a bug where a flaked episode in eztv cause the addon to fail
loading series.
for example in Doctor Who, when trying to load, eztv shows it have
episode from season 28, which is from a different Doctor Who series, and
while searching for this episode in thetvdb it crashes and wont load the
series, i added a statement to check and ignore such episodes if the
season does not exists