Sort by router ref seems to be broken

[angel-popov]

I had routers with these refs:

Request method: GET
Request URI:    http://192.168.1.166:8080/comms-router-web/api/routers?sort=-ref
Proxy:          <none>
Request params: <none>
Query params:   <none>
Form params:    <none>
Path params:    query=sort=-ref
Headers:        Accept=*/*
                Content-Type=application/json; charset=UTF-8
Cookies:        <none>
Multiparts:     <none>
Body:           <none>

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Next-Token: Um91dGVyOjE4MSxyZWY6bnVsbA
Content-Type: application/json
Content-Length: 598
Date: Tue, 27 Feb 2018 09:12:56 GMT

[
    {
        "ref": "zXhpzXEEtuaONxCxoJRuD3"
    },
    {
        "ref": "zsxhTtDe4HjRMvVjHJKf91",
        "name": "default",
        "description": "longName ??? ??????? ?? ????????345678901234567890longName ??? ??????? ?? ????????345678901234567890"
    },
    {
        "ref": "yyeAIhfXtpxtW27NSokhK6"
    },
    {
        "ref": "YxtUeWY2AXtY0uJIJ2dhn"
    },
    {
        "ref": "yvKFqvSVfHlWV2aGF5dNX5"
    },
    {
        "ref": "YS6StMgtnaGaghGrgCjvI4"
    },
    {
        "ref": "YnAXBfnFCzpMfqVSaqNgm4"
    },
    {
        "ref": "YFqhIXDPWzdBND8nw8f1A2"
    },
    {
        "ref": "ydOGvhLTru1hrvC6M4YQW5",
        "name": "default",
        "description": "longName ??? ??????? ?? ????????345678901234567890longName ??? ??????? ?? ????????345678901234567890"
    },
    {
        "ref": "Xz6lQm6IXs7Xhw7GLNGpP5"
    }
]

The id's are not sorted