Invitation flow without email fails bad

Although it is logical to add the email-address attribute field for an Invitation style flow, it is not enforced, probably because additional sources could be added to supply an email address (although unlikely for OrgIdentity and before sending the invite...).

If an email address is missing, the send-invite steps fails with an error message:

"(Org Identity ) has no known email address. Add an email address and then try again."

And the log file indicates:

{{2018-12-18 13:43:08 Notice: Notice (8): Undefined variable: vv_co_invite in [/opt/comanage/comanage/app/View/CoPetitions/send_confirmation.ctp, line 41]
Trace:
ErrorHandler::handleError() - CORE/Cake/Error/ErrorHandler.php, line 230
include - APP/View/CoPetitions/send_confirmation.ctp, line 41
View::_evaluate() - CORE/Cake/View/View.php, line 971
View::_render() - CORE/Cake/View/View.php, line 933
View::render() - CORE/Cake/View/View.php, line 473
Controller::render() - CORE/Cake/Controller/Controller.php, line 963
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 200
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 167
[main] - APP/webroot/index.php, line 96}}