From cdc017bc6349cfb29944e7da4657c2ba42f122fd Mon Sep 17 00:00:00 2001
From: Charles Haley <>
Date: Sun, 9 Jan 2011 16:42:28 +0000
Subject: [PATCH] Fix #8244 Merging two books fails (None custom numeric values
 throws exception)

---
 src/calibre/library/custom_columns.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/calibre/library/custom_columns.py b/src/calibre/library/custom_columns.py
index d925f7c91d..d905f6d01a 100644
--- a/src/calibre/library/custom_columns.py
+++ b/src/calibre/library/custom_columns.py
@@ -151,6 +151,8 @@ class CustomColumns(object):
             return v
 
         def adapt_number(x, d):
+            if x is None:
+                return None
             if isinstance(x, (str, unicode, bytes)):
                 if x.lower() == 'none':
                     return None