From 336fdba9edb39974dcde7be7c314c473c462e0ef Mon Sep 17 00:00:00 2001
From: Adrian Sampson <adrian@radbox.org>
Date: Tue, 20 Jun 2017 16:31:00 -0400
Subject: [PATCH] Musical key field may be None

Fixes a `modify` test, of all things.
---
 beets/library.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/beets/library.py b/beets/library.py
index 748f532a5..f294e6d4f 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -205,6 +205,8 @@ class MusicalKey(types.String):
         r'bb': 'a#',
     }
 
+    null = None
+
     def parse(self, key):
         key = key.lower()
         for flat, sharp in self.ENHARMONIC.items():