Description

Originally found by @jordesign this is a Gutenberg UX bug not a theme implementation issue. There is no clear programmatic fix, I think we need a better state for this edge case:

Step-by-step reproduction instructions

• user has no pages
• user has no menus
• user switches to a block theme
• user sees the error message: "Page List: Cannot Retrieve Pages." in the editor
• nothing is rendered on the front end

Screenshots, screen recording, code snippet

Editor

Rendered site

Proposed solution

Situation: the menu that’s ref’ed is deleted.

Result: Page List is shown in the canvas, an error message is shown in the inspector, with two buttons:

“Keep pages”, it keeps the page list, removes the ref, marks the document dirty.
“Create menu”, creates a new menu, updates the ref, marks the document dirty.