3.0: Nested Rich text widgets break after initial creation

[stuartromanek]

To Reproduce

1. Use theme-build https://github.com/apostrophecms/a3-demo/tree/theme-build
2. Install, login, etc
3. On the homepage, add a Two Column widget
4. Save the initial modal with two empty areas
5. In one of the two new areas, add a Rich Text widget .. add content to this widget (success)
6. Refresh the page and re-edit the rich text widget, see it lose focus and call its UPDATE event after a keystroke or two

Expected behavior

Editing rich text in a nested widget should behave

Describe the bug

A clear and concise description of what the bug is.