invalid object ids should not cause 500 error

[conord33]

Invalid object ids should not cause a 500 error.
This is happening when a non mongoId is passed into a restRsource endpoint.
#0 /Applications/MAMP/htdocs/typetees/server/api/mabi/MongoDataConnection.php(75): MongoId->__construct('52791339a8cfa08...')
#1 /Applications/MAMP/htdocs/typetees/server/api/mabi/Model.php(339): MABI\MongoDataConnection->convertToNativeId('52791339a8cfa08...')
#2 /Applications/MAMP/htdocs/typetees/server/api/mabi/RESTModelController.php(80): MABI\Model->findById('52791339a8cfa08...')
#3 [internal function]: MABI\RESTModelController->_readModel(Object(Slim\Route))
#4 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Router.php(168): call_user_func_array(Array, Array)
#5 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Slim.php(1222): Slim\Router->dispatch(Object(Slim\Route))
#6 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Middleware/Flash.php(86): Slim\Slim->call()
#7 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Middleware/MethodOverride.php(94): Slim\Middleware\Flash->call()
#8 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Middleware/PrettyExceptions.php(67): Slim\Middleware\MethodOverride->call()
#9 /Applications/MAMP/htdocs/typetees/server/api/mabi/Slim/Slim.php(1174): Slim\Middleware\PrettyExceptions->call()
#10 /Applications/MAMP/htdocs/typetees/server/api/mabi/App.php(129): Slim\Slim->run()
#11 /Applications/MAMP/htdocs/typetees/server/api/api/webroot/index.php(6): MABI\App->run()
#12 {main}