Bluesky: external embeds with null `title`

[snarfed]

title isn't nullable in app.bsky.embed.external#external. Example: https://atproto.tools/records?seq=887152670

{
  "$type": "app.bsky.feed.post",
  "bridgyOriginalText": "<span>Need a node? Ping Dimi. <br></span><span><br>RE: </span><a href=\"https://coracle.social/nevent1qqs2h8wdrkwrru75zm3we7apeqshpcpn0awglxqg80033hyymf984zgpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsygqlsvxasagnpvf5l0ely7nfamxcvyayn96g5ud45fc6wx07hts5a5psgqqqqqqsrza73v\">https://coracle.social/nevent1qqs2h8wdrkwrru75zm3we7apeqshpcpn0awglxqg80033hyymf984zgpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsygqlsvxasagnpvf5l0ely7nfamxcvyayn96g5ud45fc6wx07hts5a5psgqqqqqqsrza73v</a>",
  "bridgyOriginalUrl": "https://coracle.social/nevent1qqs0axwvssn0f4pa4u6ud3ngg63u4l8d75f20ykhajsn207xdu4txzgprpmhxue69uhhyetvv9ujumt0d4hhxarj9ecxjmntquua7e",
  "createdAt": "2024-08-05T01:13:51.000Z",
  "embed": {
    "$type": "app.bsky.embed.external",
    "external": {
      "$type": "app.bsky.embed.external#external",
      "description": "",
      "title": null,
      "uri": "https://momostr.pink/notes/note14wwu68vux8eag9hzana6rjppwrsrxl6u37vqsw7lrrwgfkj202ysqgh7dh"
    }
  },
  "text": "Need a node? Ping Dimi.\n\nRE: <https://coracle.social/nevent1qqs2h8wdrkwrru75zm3we7apeqshpcpn0awglxqg80033hyymf984zgpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsygqlsvxasagnpvf5l0ely7nfamxcvyayn96g5ud45fc6wx07hts5a5psgqqqqqqsrza73v>"
}