regexp routes fail if captures are unnamed

The following results in an error:

dispatch('^/(\d+)', 'my_func');

Giving the parameters names fixes this problem:

dispatch(array('^/(\d+)', array('num')), 'my_func');

The error occurs inside route_find after a match when trying to build $params. $route['names'] is empty, so the array_combine fails.

Found in version 4d7a09f30a84344314ebbb5ad889c9a75aa1a6cd with PHP v5.2.8