[balsa/wip/gtk4] Fix the build

[Peter Bloomfield <peterb src gnome org>]

commit ae4dbceb0896a18caa9db0596da296593ec32ff1
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Tue Jun 26 12:42:01 2018 -0400

    Fix the build

 libbalsa/mailbox.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/libbalsa/mailbox.c b/libbalsa/mailbox.c
index 6f13fa7fc..88a1be5fd 100644
--- a/libbalsa/mailbox.c
+++ b/libbalsa/mailbox.c
@@ -512,7 +512,7 @@ libbalsa_mailbox_finalize(GObject *object)
 
     libbalsa_mailbox_view_free(priv->view);
 
-    G_OBJECT_CLASS(parent_class)->finalize(object);
+    G_OBJECT_CLASS(libbalsa_mailbox_parent_class)->finalize(object);
 }
 
 
@@ -895,7 +895,7 @@ lbm_run_filters_on_reception_idle_cb(LibBalsaMailbox *mailbox)
 
     libbalsa_lock_mailbox(mailbox);
 
-    mailbox->run_filters_idle_id = 0;
+    priv->run_filters_idle_id = 0;
 
     if (!priv->filters_loaded) {
         config_mailbox_filters_load(mailbox);
@@ -997,9 +997,11 @@ lbm_run_filters_on_reception_idle_cb(LibBalsaMailbox *mailbox)
 void
 libbalsa_mailbox_run_filters_on_reception(LibBalsaMailbox *mailbox)
 {
+    LibBalsaMailboxPrivate *priv = libbalsa_mailbox_get_instance_private(mailbox);
+
     g_return_if_fail(LIBBALSA_IS_MAILBOX(mailbox));
 
-    mailbox->run_filters_idle_id =
+    priv->run_filters_idle_id =
         g_idle_add((GSourceFunc) lbm_run_filters_on_reception_idle_cb, mailbox);
 }