fix(ui): render HTML body error responses as blank pages

[ChristophWurst]

'none' would actually render the Nextcloud headers (app menu etc). This only shows our HTML.

Fixes

Error: lib/Controller/MessagesController.php:585:6: InvalidArgument: Argument 4 of OCP\AppFramework\Http\TemplateResponse::__construct expects ''|'base'|'error'|'guest'|'public'|'user', but 'none' provided (see https://psalm.dev/004)
Error: lib/Controller/MessagesController.php:639:5: InvalidArgument: Argument 4 of OCP\AppFramework\Http\TemplateResponse::__construct expects ''|'base'|'error'|'guest'|'public'|'user', but 'none' provided (see https://psalm.dev/004)

Ref nextcloud/server#57859

[kesselb]

Suggested change

	''
	TemplateResponse::RENDER_AS_BLANK,

[kesselb]

Suggested change

	''
	TemplateResponse::RENDER_AS_BLANK,

[kesselb]

/backport to stable5.7

[kesselb]

/backport to stable5.6

[kesselb]

/backport to stable5.7

[backportbot]

The backport to stable5.7 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable5.7
git pull origin stable5.7

# Create the new backport branch
git checkout -b backport/12348/stable5.7

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick a391abad

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/12348/stable5.7

Error: Failed to check for changes with origin/stable5.7: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[kesselb]

/backport to stable5.6