When I check the same it browser's Network tab it simply try to call "/" as document as in below image
then I try to further analyse the dispatcher log I see with correct url it was looking for regular path in cache but with wrong url(with double slash) it try to look some thing strange to me like
You should be redirecting these requests (ending with //) to 404 page at the apache/dispatcher level. Any specific requirement that you want to allow these pages?