Adding CO Enrollment Attribute Throws Error

Submitting https://demo.co.internet2.edu/registry/co_enrollment_attributes/add/coef:2 generates

Warning (2): Illegal string offset '' [APP/Lib/lang.php, line 524]

Code Context
// XXX need to figure out how to pass arbitrary # of args to sprintf

$s = (isset($index) ? $cm_texts[ $cm_lang ][$key][$index] : $cm_texts[ $cm_lang ][$key]);

_txt - APP/Lib/lang.php, line 524
StandardController::add() - APP/Controller/StandardController.php, line 95
CoEnrollmentAttributesController::add() - APP/Controller/CoEnrollmentAttributesController.php, line 68
ReflectionMethod::invokeArgs() - [internal], line ??
Controller::invokeAction() - CORE/Cake/Controller/Controller.php, line 473
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 104
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 86
[main] - APP/webroot/index.php, line 96

Note the save is successful.