`Tag.id` may be empty and is not documented as such

[nikclayton]

https://docs.joinmastodon.org/entities/Tag/#id is documented as "ID of the hashtag in the database. Useful for constructing URLs for the moderation tools & Admin API." and "String (cast from an integer but not guaranteed to be a number)".

This may be the empty string, which is not documented anywhere. For example, send a request for non-existent tag (https://mastodon.social/api/v1/tags/pO8WHFw3JSGvLAt0iyQ08g) and you get back:

{
    "id": "",
    "name": "pO8WHFw3JSGvLAt0iyQ08g",
    "url": "https://mastodon.social/tags/po8whfw3jsgvlat0iyq08g",
    "history": [
        {
            "day": "1773187200",
            "accounts": "0",
            "uses": "0"
        },
// ...
}