Yeah, that's strange. I'm also seeing an empty post ... almost as if it had been deleted.
EDIT: The cause seems to have been a bad interaction between the output you posted and one of the extensions that handle the formatting of posts. It's generally a good idea to set such blocks of output off as code, so it won't be affected by any formatting. Just add a line consisting entirely of three backticks ...
```
... above and below the section that shouldn't be formatted. (Or you can use the BBcode code tags, if you like.)
I've fixed the post above; you should be able to edit it now. Should this happen again in the future, just navigate to another page immediately ... click the Flarum logo or something. You should then see the minimized composer frame at the bottom of the page; click on that to open it and edit the post.
