Fast render fails when post contains passthrough <script> tags

[rorosaurus]

1. Make a post which contains +++<script>document.write("Hello!");</script>+++
2. Enable fast render

The whole wrapper for the admin console will disappear and you'll see a blank page with the text "Hello!"

The post itself is published fine though, it seems. So this should be a low priority bug, if it meets the bar at all. :)