Unable to delete empty key document

[Alex Ivasyuv]

hi,

I found an issue? in Futon, when there exist an record with empty key 
(""), it's unable to delete it.
Record looks like:
""             {rev: "1-8d76c8a85c9ad91083a200bf86e64c6a"}
But from command like when you try to delete it, it'll delete entire 
your db!
$ curl -X DELETE http://localhost:5984/mydb/""; -d {rev: 
1-8d76c8a85c9ad91083a200bf86e64c6a}