"iframeBody is null" error occurs after publishing a Landing page with a schedule block.

Prereq. : Use Firefox.

Steps:
1. Create new LP with first layout.
2. Add schedule block, leave hero.
3. Add blog post "Why we love NYC".
4. Change airtime to 21/12/2017 16:45.
5. Scroll the page while still in edit mode (seems crucial, example attached).
6. Publish.
Actual: "iframeBody is null" error occurs (attached).
Expected: No errors occur.

Remarks: Cannot reproduce on Chrome.