Managerless Bayern Munich thrashed Borussia Dortmund 4-0 in 'Der Klassiker' on Saturday as Robert Lewandowski continued his phenomenal scoring run with two goals at the Allianz Arena. Serge Gnabry claimed Bayern's second, while visiting captain Mats Hummels scored a late own goal for his former club as Dortmund suffered another heavy defeat in Munich, where they also lost 5-0 in …