[balsa] mailbox-local: Use g_ptr_array_set_size()

[Peter Bloomfield <peterb src gnome org>]

commit 7ba0b34b53bd39b490b1262f4bd96819dcf18963
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Wed Feb 5 17:25:19 2020 -0500

    mailbox-local: Use g_ptr_array_set_size()
    
    instead of adding NULL pointers in a loop.

 libbalsa/mailbox_local.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/libbalsa/mailbox_local.c b/libbalsa/mailbox_local.c
index 8f3290772..fb077ad2b 100644
--- a/libbalsa/mailbox_local.c
+++ b/libbalsa/mailbox_local.c
@@ -1016,8 +1016,8 @@ lbm_local_cache_message(LibBalsaMailboxLocal * local,
     if (!priv->threading_info)
         return;
 
-    while (priv->threading_info->len < msgno)
-        g_ptr_array_add(priv->threading_info, NULL);
+    if (priv->threading_info->len < msgno)
+        g_ptr_array_set_size(priv->threading_info, msgno);
     entry = &g_ptr_array_index(priv->threading_info, msgno - 1);
 
     if (*entry)