#337 Default workflow participant to role owner if user not found

[George Steimer]

If the tripped user is not found in the repository, the code should default the task owner to the role owner. When attaching documents to the form, the code fails with a NPE because it assumes the user will always exist.

We should ensure that the role owner is defaulted to correctly in both cases - workflow documents attached and not attached. When workflow documents are attached, the adXML should be created correctly and the role owner should be able to sign off properly.