fix(ui): allow canceling jats generation
Closes #1019 (closed). When the modal was in a loading state, the close button was not hooked up. Now it cancels generation.
This also fixes another issue. If a manuscript does not have a supported document view (if it was a URL), we still show the Production view, with the "No supported view of a file". We were also showing the download dropdown button, which was causing an error because it was not given a manuscript ID. I've removed that.