…o-gitea#24485)

Backport go-gitea#24444 by @silverwind

Remove the
[renderWhitespace](https://microsoft.github.io/monaco-editor/docs.html#interfaces/editor.IEditorOptions.html#renderWhitespace)
override, so the default value of `selection` takes over and makes
whitespace visible on selection.

<img width="128" alt="Screenshot 2023-04-30 at 19 09 41"
src="https://user-images.githubusercontent.com/115237/235366707-d598268d-03cc-4839-a195-c460bddae99b.png">

Co-authored-by: silverwind <me@silverwind.io>

On the @forgejo instance of Codeberg, we discovered that forking a repo
which is already forked now returns a 500 Internal Server Error, which
is unexpected. This is an attempt at fixing this.

The error message in the log:
~~~
2023/05/02 08:36:30 .../api/v1/repo/fork.go:147:CreateFork() [E]
[6450cb8e-113] ForkRepository: repository is already forked by user
[uname: ...., repo path: .../..., fork path: .../...]
~~~

The service that is used for forking returns a custom error message
which is not checked against.

About the order of options:
The case that the fork already exists should be more common, followed by
the case that a repo with the same name already exists for other
reasons. The case that the global repo limit is hit is probably not the
likeliest.

Co-authored-by: Otto Richter <otto@codeberg.org>
Co-authored-by: Giteabot <teabot@gitea.io>