ui/dbus: fix leak on message filtering

A filter function that wants to drop a message should return NULL, in
which case it must also unref the message itself.

Fixes: fa88b85 ("ui/dbus: filter out pending messages when scanout")

Signed-off-by: Marc-André Lureau <[email protected]>
Reviewed-by: Akihiko Odaki <[email protected]>
Message-ID: <[email protected]>
(cherry picked from commit 244d52f)
Signed-off-by: Michael Tokarev <[email protected]>

ui/dbus-listener.c

@@ -1001,6 +1001,7 @@ dbus_filter(GDBusConnection *connection,
     serial = g_dbus_message_get_serial(message);
     if (serial <= ddl->out_serial_to_discard) {
         trace_dbus_filter(serial, ddl->out_serial_to_discard);
+        g_object_unref(message);
         return NULL;
     }