From dc3cc18bf0c649dfdb280a7afbb3b6039101f281 Mon Sep 17 00:00:00 2001
From: David Bremner <david@tethera.net>
Date: Mon, 3 Sep 2018 18:02:25 -0300
Subject: [PATCH] lib: add _notmuch_message_list_empty

There is no public notmuch_message_list_t public interface, so to this
is added to the private API. We use it immediately in thread.cc;
future commits will use it further.
---
 lib/messages.c        | 9 +++++++++
 lib/notmuch-private.h | 3 +++
 lib/thread.cc         | 2 +-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/messages.c b/lib/messages.c
index a88f974f..ba8a9777 100644
--- a/lib/messages.c
+++ b/lib/messages.c
@@ -56,6 +56,15 @@ _notmuch_message_list_add_message (notmuch_message_list_t *list,
     list->tail = &node->next;
 }
 
+bool
+_notmuch_message_list_empty (notmuch_message_list_t *list)
+{
+    if (list == NULL)
+	return TRUE;
+
+    return (list->head == NULL);
+}
+
 notmuch_messages_t *
 _notmuch_messages_create (notmuch_message_list_t *list)
 {
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 02cc0e09..590a3451 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -477,6 +477,9 @@ struct _notmuch_messages {
 notmuch_message_list_t *
 _notmuch_message_list_create (const void *ctx);
 
+bool
+_notmuch_message_list_empty (notmuch_message_list_t *list);
+
 void
 _notmuch_message_list_add_message (notmuch_message_list_t *list,
 				   notmuch_message_t *message);
diff --git a/lib/thread.cc b/lib/thread.cc
index 6d15c49b..a0ce4be3 100644
--- a/lib/thread.cc
+++ b/lib/thread.cc
@@ -425,7 +425,7 @@ _resolve_thread_relationships (notmuch_thread_t *thread)
     if (first_node) {
 	message = first_node->message;
 	in_reply_to = _notmuch_message_get_in_reply_to (message);
-	if (thread->toplevel_list->head &&
+	if (! _notmuch_message_list_empty (thread->toplevel_list) &&
 	    in_reply_to && strlen (in_reply_to) &&
 	    g_hash_table_lookup_extended (thread->message_hash,
 					  in_reply_to, NULL,