Hello folks
it's been now more than a year of using this system without any problem. for now 2 months i have strange error line that appears on the admin page, and now new pilots registration cannot be validated.
the error message is below
Error: An Internal Error Has Occurred.
Notice (

: compact() [function.compact]: Undefined variable: subject [CORE/Cake/Utility/ObjectCollection.php, line 128]
Notice (

: compact() [function.compact]: Undefined variable: subject [CORE/Cake/Utility/ObjectCollection.php, line 128]
Stack Trace
CORE/Cake/Network/Email/MailTransport.php line 52 → MailTransport->_mail(string, string, string, string, null)
CORE/Cake/Network/Email/CakeEmail.php line 1173 → MailTransport->send(CakeEmail)
APP/Controller/GvausersController.php line 116 → CakeEmail->send(string)
[internal function] → GvausersController->edit(string)
CORE/Cake/Controller/Controller.php line 491 → ReflectionMethod->invokeArgs(GvausersController, array)
CORE/Cake/Routing/Dispatcher.php line 193 → Controller->invokeAction(CakeRequest)
CORE/Cake/Routing/Dispatcher.php line 167 → Dispatcher->_invoke(GvausersController, CakeRequest)
APP/webroot/index.php line 110 → Dispatcher->dispatch(CakeRequest, CakeResponse)