Tweak logic since now both cover_file and art_file may return None.

Author: E.S. Rosenberg a.k.a. Keeper of the Keys

src/gpodder/coverart.py

@@ -49,13 +49,14 @@ def get_cover(self, podcast, download=False, episode=None):
             # Get episode art.
             filename = episode.art_file
             cover_url = episode.episode_art_url
-            if not cover_url:
-                return None
         else:
             # Get podcast cover.
             filename = podcast.cover_file
             cover_url = podcast.cover_url
 
+        if not cover_url:
+            return None
+
         username = podcast.auth_username
         password = podcast.auth_password