uninformative output error message

[Removed by request]

A stack was created successfully from a template that is missing "resources:" but has "outputs:". stack-show shows those outputs like so:
"output_value": null,
"output_error": "The specified reference \"private_subnet\" (in unknown) is incorrect.",
"description": "No description given",
"output_key": "private_network"

Template: http://paste.openstack.org/show/138136/

Version: 0.2.10

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/137552

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/137552
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=514916125b08097eaf633fb11dbe979af1cf69ae
Submitter: Jenkins
Branch: master

commit 514916125b08097eaf633fb11dbe979af1cf69ae
Author: Peter Razumovsky <email address hidden>
Date: Thu Nov 27 11:52:58 2014 +0300

    Fix outputs validation place in Stack.validate

    Because of outputs validation check located in
    wrong place, outputs validation skipped, when
    template has no resources. It's incorrect because
    of possible incorrect references to unknown resources.

    Change-Id: I693b51540b0678aa17b861b9f85a0cb2a9552660
    Closes-bug: #1396441