Custom Placeholder Token Matching on optional token

[bkdotcom]

https://github.com/auraphp/Aura.Router/blob/3.x/docs/defining-routes.md#custom-placeholder-token-matching

tweaking the supplied example so that date is optional (and even supplying a default date)

<?php
$map->get('/calendar{/date}')
    ->tokens([
        'date' => function ($date, $route, $request) {
            try {
                new \DateTime($date);
                return true;
            } catch(\Exception $e) {
                return false;
            }
        }
    ])
    ->defaults(['date'=>'yesterday']);

will throw a notice: vendor/aura/router/src/Rule/Path.php (line 89): = Undefined index: date

notice is thrown even when supplying a default date value.