[glib] gdbusmessage: Fix a minor memory leak on an error path

[Philip Withnall <pwithnall src gnome org>]

commit bc01109618009ad748abdc58bdc0c64891b84db0
Author: Philip Withnall <philip tecnocode co uk>
Date:   Tue Apr 21 23:57:17 2015 +0100

    gdbusmessage: Fix a minor memory leak on an error path
    
    If g_dbus_message_to_blob() fails at all, it will leak its mbuf. Spotted
    by running the gdbus-serialization test under Valgrind — so there is a
    justification for leak-free tests after all!

 gio/gdbusmessage.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gio/gdbusmessage.c b/gio/gdbusmessage.c
index 766609e..d9d8f37 100644
--- a/gio/gdbusmessage.c
+++ b/gio/gdbusmessage.c
@@ -2745,6 +2745,9 @@ g_dbus_message_to_blob (GDBusMessage          *message,
   ret = (guchar *)mbuf.data;
 
  out:
+  if (ret == NULL)
+    g_free (mbuf.data);
+
   return ret;
 }