[youku] Add test case.

Some playlist has no data-id value.

Change-Id: I97455f2907f08bda03b538cdc13ec827e2f8ce26

youtube_dl/extractor/youku.py

@@ -241,6 +241,10 @@ class YoukuShowIE(InfoExtractor):
         # Ongoing playlist. The initial page is the last one
         'url': 'http://list.youku.com/show/id_za7c275ecd7b411e1a19e.html',
         'only_matching': True,
+    }, {
+        #  No data-id value.
+        'url': 'http://list.youku.com/show/id_zefbfbd61237fefbfbdef.html',
+        'only_matching': True,
     }]
 
     def _extract_entries(self, playlist_data_url, show_id, note, query):