[balsa] mailbox_maildir: do not unref a NULL GMimeMessage

[Peter Bloomfield <peterb src gnome org>]

commit 7f3df7e1d27706f93d8615199eea7a901f8eee06
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Wed Jul 17 22:59:54 2019 -0400

    mailbox_maildir: do not unref a NULL GMimeMessage
    
    * libbalsa/mailbox_maildir.c
      (libbalsa_mailbox_maildir_fetch_message_structure): do not unref
      a NULL GMimeMessage.

 ChangeLog                  | 6 ++++++
 libbalsa/mailbox_maildir.c | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/ChangeLog b/ChangeLog
index 3b3236855..000e3868c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-07-17  Peter Bloomfield  <pbloomfield bellsouth net>
+
+       * libbalsa/mailbox_maildir.c
+       (libbalsa_mailbox_maildir_fetch_message_structure): do not unref
+       a NULL GMimeMessage.
+
 2019-07-17  Peter Bloomfield  <pbloomfield bellsouth net>
 
        * libbalsa/gmime-part-rfc2440.c (g_mime_part_check_rfc2440): use
diff --git a/libbalsa/mailbox_maildir.c b/libbalsa/mailbox_maildir.c
index 0e56d0b14..cb731dba0 100644
--- a/libbalsa/mailbox_maildir.c
+++ b/libbalsa/mailbox_maildir.c
@@ -837,7 +837,8 @@ libbalsa_mailbox_maildir_fetch_message_structure(LibBalsaMailbox * mailbox,
                                                    msg_info->subdir,
                                                    msg_info->filename);
         libbalsa_message_set_mime_message(message, mime_message);
-        g_object_unref(mime_message);
+        if (mime_message != NULL)
+            g_object_unref(mime_message);
     }
 
     return LIBBALSA_MAILBOX_CLASS(libbalsa_mailbox_maildir_parent_class)->