migration: fix vmdesc leak on vmstate_save() error

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190912122514.22504-2-marcandre.lureau@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
diff --git a/migration/qjson.h b/migration/qjson.h
index 41664f2..1786bb5 100644
--- a/migration/qjson.h
+++ b/migration/qjson.h
@@ -24,4 +24,6 @@
 const char *qjson_get_str(QJSON *json);
 void qjson_finish(QJSON *json);
 
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(QJSON, qjson_destroy)
+
 #endif /* QEMU_QJSON_H */