From 1077c71c2ed2bd0cf9a9e117f1a4692c9aa78bfc Mon Sep 17 00:00:00 2001
From: Damien Elmes <git@ichi2.net>
Date: Sun, 8 Apr 2012 21:39:04 +0900
Subject: [PATCH] don't throw error in half-complete field filter

---
 anki/template/template.py | 3 ++-
 tests/test_collection.py  | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/anki/template/template.py b/anki/template/template.py
index 8a6e9aec0..f3bec9e66 100644
--- a/anki/template/template.py
+++ b/anki/template/template.py
@@ -186,7 +186,8 @@ class Template(object):
                 return ""
         else:
             # hook-based field modifier
-            txt = runFilter('fmod_' + mod, txt, extra, context, tag, tag_name);
+            txt = runFilter('fmod_' + mod, txt or '', extra, context,
+                            tag, tag_name);
             if txt is None:
                 return '{unknown field %s}' % tag_name
             return txt
diff --git a/tests/test_collection.py b/tests/test_collection.py
index cb175ee4f..7e610dd8c 100644
--- a/tests/test_collection.py
+++ b/tests/test_collection.py
@@ -147,6 +147,7 @@ def test_furigana():
     deck = getEmptyDeck()
     mm = deck.models
     m = mm.current()
+    # filter should work
     m['tmpls'][0]['qfmt'] = '{{kana:Front}}'
     mm.save(m)
     n = deck.newNote()
@@ -154,6 +155,11 @@ def test_furigana():
     deck.addNote(n)
     c = n.cards()[0]
     assert c.q().endswith("abc")
+    # and should avoid sound
     n['Front'] = 'foo[sound:abc.mp3]'
     n.flush()
     assert "sound:" in c.q(reload=True)
+    # it shouldn't throw an error while people are editing
+    m['tmpls'][0]['qfmt'] = '{{kana:}}'
+    mm.save(m)
+    c.q(reload=True)