From 0dc08bbacc8f35e81c4281eb022f339e388535ab Mon Sep 17 00:00:00 2001
From: Damien Elmes <git@ichi2.net>
Date: Sun, 8 Jan 2017 20:47:26 +1000
Subject: [PATCH] fix error appearing when undo shortcut pressed when nothing
 to undo

---
 aqt/main.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/aqt/main.py b/aqt/main.py
index 24ea6d27e..474919f73 100644
--- a/aqt/main.py
+++ b/aqt/main.py
@@ -682,6 +682,8 @@ title="%s" %s>%s</button>''' % (
 
     def onUndo(self):
         n = self.col.undoName()
+        if not n:
+            return
         cid = self.col.undo()
         if cid and self.state == "review":
             card = self.col.getCard(cid)