[PATCH] Fix error reporting in notmuch_database_find_message_by_filename

[Justus Winter <4winter@informatik.uni-hamburg.de>]

Formerly it was possible for *message_ret to be left
uninitialized. The documentation however clearly states that "[o]n any
failure or when the message is not found, this function initializes
'*message' to NULL".

Signed-off-by: Justus Winter <4winter@informatik.uni-hamburg.de>
---
 lib/database.cc |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/lib/database.cc b/lib/database.cc
index 8f8df1a..16c4354 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -1825,6 +1825,9 @@ notmuch_database_find_message_by_filename (notmuch_database_t *notmuch,
     if (message_ret == NULL)
 	return NOTMUCH_STATUS_NULL_POINTER;
 
+    /* return NULL on any failure */
+    *message_ret = NULL;
+
     local = talloc_new (notmuch);
 
     try {
-- 
1.7.9.1