If the resource registry data from a loaded file is None the method will
stacktrace resulting in a deployment failure. This change will ensure
that the data is loaded and in the event the resource_registry option is
None, it will set an empty set and carry on.
Change-Id: I09413d8b17657e9aeb38bc5a2d9ed44182ddf539
Signed-off-by: Kevin Carter <kecarter@redhat.com>