From cc31246f08d0eb5619682bd54d33dfd05cb1abf7 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 16 Jun 2011 18:09:56 -0600
Subject: [PATCH] Fix #798441 (Download Metadata hangs Calibre)

---
 src/calibre/gui2/metadata/single.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/calibre/gui2/metadata/single.py b/src/calibre/gui2/metadata/single.py
index b62aa28a68..d818f2db2a 100644
--- a/src/calibre/gui2/metadata/single.py
+++ b/src/calibre/gui2/metadata/single.py
@@ -388,6 +388,10 @@ class MetadataSingleDialogBase(ResizableDialog):
 
     def apply_changes(self):
         self.changed.add(self.book_id)
+        if self.db is None:
+            # break_cycles has already been called, don't know why this should
+            # happen but a user reported it
+            return True
         for widget in self.basic_metadata_widgets:
             try:
                 if not widget.commit(self.db, self.book_id):