[PATCH] fix typo in Tags.__len__

[Cédric Cabessa]

Here is a sample that trigger the bug :
"""
import notmuch
db = notmuch.Database()
query = db.create_query("tag:inbox")

for m in query.search_messages():
    len(m.get_tags())

"""
---
 bindings/python/notmuch/tag.py |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/bindings/python/notmuch/tag.py b/bindings/python/notmuch/tag.py
index 65a9118..2f82c1a 100644
--- a/bindings/python/notmuch/tag.py
+++ b/bindings/python/notmuch/tag.py
@@ -116,8 +116,8 @@ class Tags(object):
             raise NotmuchError(STATUS.NOT_INITIALIZED)
 
         i=0
-        while nmlib.notmuch_tags_valid(self._msgs):
-            nmlib.notmuch_tags_move_to_next(self._msgs)
+        while nmlib.notmuch_tags_valid(self._tags):
+            nmlib.notmuch_tags_move_to_next(self._tags)
             i += 1
         self._tags = None
         return i
-- 
1.7.6