lib/n_m_g_filename: catch Xapian exceptions, document NULL return

This is the same machinery as applied for

     notmuch_message_get_{thread,message}_id

2 files changed, 8 insertions, 1 deletions

diff --git a/lib/message.cc b/lib/message.cc
index 0551a427..1a9eaffe 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -1122,7 +1122,12 @@ _notmuch_message_ensure_filename_list (notmuch_message_t *message)
 const char *
 notmuch_message_get_filename (notmuch_message_t *message)
 {
-    _notmuch_message_ensure_filename_list (message);
+    try {
+	_notmuch_message_ensure_filename_list (message);
+    } catch (Xapian::Error &error) {
+	LOG_XAPIAN_EXCEPTION (message, error);
+	return NULL;
+    }
 
     if (message->filename_list == NULL)
 	return NULL;
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 037913f4..5c17ec7c 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -1433,6 +1433,8 @@ notmuch_message_count_files (notmuch_message_t *message);
  * this function will arbitrarily return a single one of those
  * filenames. See notmuch_message_get_filenames for returning the
  * complete list of filenames.
+ *
+ * This function returns NULL if it triggers a Xapian exception.
  */
 const char *
 notmuch_message_get_filename (notmuch_message_t *message);