Google Calendar Block: block stops displaying when page turns to draft

This might be a bit of an edge case, but Google Calendar block added to hompepage stopped displaying in both editor and on the frontend when I switched themes. This happened only with Varia child themes, so might have to do with turning current homepage into a draft on theme switch.

#### Steps to reproduce the issue

1. Activate one of Varia child themes (for example Maywood)
2. Add Google Calendar block to the homepage.
3. Switch themes to a different Varia child theme (for example Barnsbury)
4. Naviagte to My Site > Pages > Drafts (previous theme homepage turns into a draft on theme switch)
5. Edit the old homepage. Notice that Google Calendar block is not visible, although there’s an empty space in its place. If you click on it, you’ll see the block controls, and the embed code is in the settings in the sidebar.
6. If at this point you switch back to the original theme, the issue with Google Calendar persists (even though the homepage status automatically returns to published from draft).
7. I tried the above steps with Calendly block, and it did not disappear on theme switch, when the homepage turned to draft.

Video of the issue: https://cloudup.com/c7GMeS-o7k8

Start by reproducing the Google Calendar block failure with Varia child themes, following the listed theme-switch and homepage draft steps in the issue. Trace the block’s editor and frontend rendering during the draft-to-published transition; done means the block remains visible in both places after switching themes and restoring the original theme.

Written by the indexing model from the issue text.