[balsa] mailbox-local: Clear idle handler id

[Peter Bloomfield <peterb src gnome org>]

commit e2bc5a28a0500f6dd78368ea426f3d2832cdb4b5
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Mon Jan 27 15:23:08 2020 -0500

    mailbox-local: Clear idle handler id
    
    when the handler is called--duh!

 libbalsa/mailbox_local.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/libbalsa/mailbox_local.c b/libbalsa/mailbox_local.c
index d62b040fb..35562d482 100644
--- a/libbalsa/mailbox_local.c
+++ b/libbalsa/mailbox_local.c
@@ -1150,6 +1150,10 @@ typedef struct {
 static gboolean
 lbml_set_threading_idle_cb(LbmlSetThreadingInfo * info)
 {
+    LibBalsaMailboxLocal *local = LIBBALSA_MAILBOX_LOCAL(info->mailbox);
+    LibBalsaMailboxLocalPrivate *priv =
+        libbalsa_mailbox_local_get_instance_private(local);
+
     libbalsa_lock_mailbox(info->mailbox);
 
     if (libbalsa_mailbox_get_msg_tree(info->mailbox) != NULL) {
@@ -1162,6 +1166,7 @@ lbml_set_threading_idle_cb(LbmlSetThreadingInfo * info)
         lbml_set_threading(info->mailbox, info->thread_type);
     }
 
+    priv->set_threading_id = 0;
     libbalsa_unlock_mailbox(info->mailbox);
     g_free(info);