[mplayer] Fix error introduced by downloader separation

youtube_dl/downloader/mplayer.py

@@ -9,6 +9,7 @@ from ..utils import (
 
 class MplayerFD(FileDownloader):
     def real_download(self, filename, info_dict):
+        url = info_dict['url']
         self.report_destination(filename)
         tmpfilename = self.temp_name(filename)