Fix submission of new topics in no-js

A workflow id is currently passed in the URL. The workflow is new still, though.
The discussion workflow is not actually created until the new post is submitted.
When attempting to submit the new topic without JS, the workflow ID in the url
will be loaded (or rather, tried to) which will fail since it doesn't yet exist.

JS was already doing this correctly, not passing a workflow id if
$workflow->isNew()

Bug: 65639
Change-Id: If2324f1ddbaeaa8d83257c70b987088186279e2e
Merge "Fix submission of new topics in no-js"