[Developers] understanding an error message

[Augusto Callejas]

hi-

when i intentionally submit this bad query:

{
  "query" : [
    {
      "id" : "/common/topic",
      "properties" : [
        {}
      ],
      "sort" : [
        null
      ],
      "type" : "/type/type"
    }
  ]
}

i get this error message:

{
  "code" : "/api/status/error",
  "messages" : [
    {
      "code" : "/api/status/error/mql/parse",
      "info" : {
        "key" : "sort"
      },
      "message" : "Can't use a dictionary as a directive value"
    }
  ]
}

i don't understand it.  what dictionary is the message referring to?
does the error message mean the array?

thanks,
augusto.