Mastodon API: relationships endpoint should never return object instead of array

[Vyr Cossont]

When relationships with multiple accounts are requested, but not all accounts have a relationship with the requesting account, the resulting array may contain gaps, and is incorrectly serialized: for example, when requesting 3 accounts like /api/v1/accounts/relationships?id%5B%5D=644249863538274110&id%5B%5D=676701638882780286&id%5B%5D=560748040462586535, and there's no relationship with the middle one, this JSON results:

{
  "0": {
    "id": "644249863538274110",
    "following": true,
    "followed_by": false,
    "blocking": false,
    "muting": false,
    "muting_notifications": null,
    "requested": false,
    "domain_blocking": null,
    "showing_reblogs": null,
    "endorsed": false
  },
  "2": {
    "id": "560748040462586535",
    "following": true,
    "followed_by": false,
    "blocking": false,
    "muting": false,
    "muting_notifications": null,
    "requested": false,
    "domain_blocking": null,
    "showing_reblogs": null,
    "endorsed": false
  }
}

The correct response in this case would be:

[
  {
    "id": "644249863538274110",
    "following": true,
    "followed_by": false,
    "blocking": false,
    "muting": false,
    "muting_notifications": null,
    "requested": false,
    "domain_blocking": null,
    "showing_reblogs": null,
    "endorsed": false
  },
  {
    "id": "560748040462586535",
    "following": true,
    "followed_by": false,
    "blocking": false,
    "muting": false,
    "muting_notifications": null,
    "requested": false,
    "domain_blocking": null,
    "showing_reblogs": null,
    "endorsed": false
  }
]

This is a classic PHP issue and can probably be fixed by calling array_values on the response to renumber it, which should cause it to be serialized as an actual array instead of an object.