Exception not caught by ZF2 - zend-framework2

Question

In the onBootstrap of my Application's Module.php I have registered a function onErrors on the EVENT_DISPATCH and EVENT_DISPATCH_ERROR events. In any of my models if I throw a custom error, Zend will catch it for me and in the onErrors function and I can handle the error (show an error page, return an error message as json, etc). This works fine except when an error is thrown in a function that's being used by Smarty. In that case I do still end up in the onErrors, but McvEvent->exception is NULL and I get this error:
Fatal error: Uncaught exception 'Application\Exception\InternalServerErrorException' in
/........../module/Smarty/src/Smarty/View/Renderer.php:90 Stack trace:
#0 /........../vendor/zendframework/zendframework/library/Zend/View/View.php(205):
Smarty\View\Renderer->render(Object(Zend\View\Model\ViewModel))
#1 /........../vendor/zendframework/zendframework/library/Zend/Mvc/View/Http/DefaultRenderingStrategy.php(102):
Zend\View\View->render(Object(Zend\View\Model\ViewModel))
#2 [internal function]:
Zend\Mvc\View\Http\DefaultRenderingStrategy->render(Object(Zend\Mvc\MvcEvent))
#3 /........../vendor/zendframework/zendframework/library/Zend/EventManager/EventManager.php(468):
call_user_func(Array, Object(Zend\Mvc\MvcEvent))
#4 /........../vendor/zendframework/zendframework/library/Zend/EventManager/EventManager.php(207):
Zend\EventManager\EventManager->triggerListeners('render.error',
Object(Zend\Mvc\MvcEvent), Array)
#5 /.......... in
/........../module/Smarty/src/Smarty/View/Renderer.php on line 90
What's happening here? Why isn't Zend catching this error for me?