Empty values also should be an array as usual

Hi all, thank you for providing security advisories.

I found some cases where an empty value has a different type than usual. For example,

$ wget https://secdb.alpinelinux.org/v3.3/community.json
$ jq . community.json
{
  "archs": [
    "x86_64",
    "x86",
    "armhf"
  ],
  "packages": {},
  "urlprefix": "http://dl-cdn.alpinelinux.org/alpine",
  "distroversion": "v3.3",
  "apkurl": "{{urlprefix}}/{{distroversion}}/{{reponame}}/{{arch}}/{{pkg.name}}-{{pkg.ver}}.apk",
  "reponame": "community"
}

As shown above, "packages" is an object, even though it is usually an array. It causes an unmarshal error in Go.

json: cannot unmarshal object into Go value of type []alpine.packages

The same issue exists in pkg as well.

   {
      "pkg": {
        "name": "heimdal",
        "secfixes": {
          "7.1.0-r1": [
            "CVE-2017-11103"
          ],
          "7.1.0-r2": [
            "CVE-2017-17439"
          ],
          "7.4.0-r0": {}
        }
      }
    },

It is possible to fix it?