lib: Fix notmuch_query_search_threads to return NULL on any Xapian exception.

Previously, if the underlying search_messages hit an exception and returned
NULL, this function would ignore that and return a non-NULL, (but empty)
threads object. Fix this to properly propagate the error.

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/query.cc b/lib/query.cc
index d241dc1d..59f4011b 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -249,6 +249,10 @@ notmuch_query_search_threads (notmuch_query_t *query)
 					      free, NULL);
 
     threads->messages = notmuch_query_search_messages (query);
+    if (threads->messages == NULL) {
+	    talloc_free (threads);
+	    return NULL;
+    }
 
     threads->thread_id = NULL;