Set proper defaults for empty documents

[hanspagel]

New documents need a good default:

[ 'type' => 'doc', 'content' => [], ]

But that would only work for tiptap?

Or maybe better shouldn’t fail like that:

Attaching to mailmaker_hocuspocus_1
hocuspocus_1  | [2021-05-05T15:14:52.962Z] Server configured …
hocuspocus_1  | [2021-05-05T15:14:52.965Z] Listening on port "80" …
hocuspocus_1  | [2021-05-05T15:15:22.160Z] Upgrading connection …
hocuspocus_1  | [2021-05-05T15:15:22.174Z] New connection to "App%5CModels%5CNewsletter%3A1" …
hocuspocus_1  | [2021-05-05T15:15:23.592Z] Created document "App%5CModels%5CNewsletter%3A1" …
hocuspocus_1  | /var/www/node_modules/prosemirror-model/dist/index.js:1368
hocuspocus_1  |   if (!json) { throw new RangeError("Invalid input for Node.fromJSON") }