If there is not transcript, there should not be a transcript element added to to the embed

[Hpmason]

Currently if there is a comic with an empty string transcript, the transcript element should not be added.

Json data:

{
    "month": "1",
    "num": 1782,
    "link": "",
    "year": "2017",
    "news": "",
    "safe_title": "Team Chat",
    "transcript": "",
    "alt": "2078: He announces that he's finally making the jump from screen+irssi to tmux+weechat.",
    "img": "https://imgs.xkcd.com/comics/team_chat.png",
    "title": "Team Chat",
    "day": "6"
}

Bug most likely occurs from this line:

xkcdbot-rs/src/embeds.rs

Line 21 in 63e6452

if self.transcript.is_empty() {

This would fail if there was whitespace added at some point during de-serialization, so requires some testing