From 8c7a9e3f958e80ca730c757796b76db97069460b Mon Sep 17 00:00:00 2001
From: Thomas Adamcik <thomas@adamcik.no>
Date: Mon, 13 Apr 2015 00:02:00 +0200
Subject: [PATCH] mpd: 'list "artist" ""' should not generate an invalid query

---
 mopidy/mpd/protocol/music_db.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mopidy/mpd/protocol/music_db.py b/mopidy/mpd/protocol/music_db.py
index fc726255..541fcd6d 100644
--- a/mopidy/mpd/protocol/music_db.py
+++ b/mopidy/mpd/protocol/music_db.py
@@ -270,10 +270,12 @@ def list_(context, *args):
     if field not in _LIST_MAPPING:
         raise exceptions.MpdArgError('incorrect arguments')
 
+    query = None
     if len(params) == 1:
         if field != 'album':
             raise exceptions.MpdArgError('should be "Album" for 3 arguments')
-        query = {'artist': params}
+        if params[0].strip():
+            query = {'artist': params}
     else:
         try:
             query = _query_from_mpd_search_parameters(params, _LIST_MAPPING)